Notification Center: New Notification System
Improved app notifications at the top
Lock screen notifications. Swipe will open related app.
Notification options to choose for each app.
Notification sorting by app, time etc.
iMessage: Text messaging between iOS devices over Wi-Fi or 3G (Similar to WhatsApp)
Newstand: Similar to iBooks to store, auto-download magazine subscriptions & new issues.
Reminders: A list of reminders with Geo-fence integrated with Calendar app
Twitter Integration: Log in to Twitter from settings once and Tweet anything from Safri, Photos, YouTube etc. Similar to login & sharing used by Mail.app
AirPlay Mirroring for iPad 2: Duplicate the iPad screen on television wirelessly
iCloud integration: A new free service with more than 5GB data to be shared between iOS devices
Open Camera.app from lock screen: Double tapping on Home button will open the Camera.app from lock screen
Take pictures from lock screen: Volume up button can be used to take pictures
Camera Grid: For more precise focus and accurate photography. This feature was available on Camera+ app
Camera Zoom: Pinch-to-zoom Gesture like Photos.app on Camera.app
One tap Auto Focus and Auto Exposure
Lock Auto Exposure & Auto Focus for consistency.
Swipe Left to open camera roll
Crop Photos: Not available on 3GS
Enhance Color tones of photos: Not available on 3GS
Rotate Photos:
Red-eye removal: Remove, correct Red-eye within Photos.app
Photo Stream via iCloud over all your iOS devices
Organize photos within Camera Roll
Tabbed Browsing in Safari: For iPad only
Safari Reader: Like RSS reader
Safari Reading List: Save web pages for offline reading
Improved Performance: Like it was enhanced in 4.3.3
Private Browsing: Similar to Firefox / Incognito on Chrome.
Website specific data can be deleted
Cut the cord: Activate and setup iOS device without a Mac or PC
Over-The-Air (OTA) iOS Software Updates: Again, no need of a computer & cord
Delta Software Updates: Upgrade only changed files. No need to download & install entire OS. (Similar to WordPress!)
Wi-Fi Sync: Sync iOS device with PC or Mac over Wi-Fi
Backup and Restore from iCloud account
Sync Exchange tasks
Downloads: See a list of downloaded apps from App Store from any of your iOS device
Rich Text Formatting for Composing Mail (Bold, Italics, Underline, etc.)
Improved offline support for Mail.app
Indentation Control
Drag-able email addresses: Drag, arrange email addresses in To, CC, BCC fields
Improved mail search: Full content search in Mail
Flag Emails
S/MIME Security
Profile picture for Game Center
Friend recommendations for Game Center
Games recommendation
Friends-of-friends list
App Store in Game Center: App store integrated within Game Center to find & buy new Apps / Games
New Achievements like Perks, Points
Play turn-based games within Game Center
Swipe-Up with 4-5 fingers for multitasking bar (iPad only)
Swipe-Left or Swipe-Right with 4-5 fingers to switch between running apps (iPad only)
Pinch with 4-5 fingers for the home screen (iPad only)
New Split keyboard: For easier typing on iPad
New Keyboard Shortcuts (Not sure what it is)
Emoji Emoticons: Emoticons like we see in IMs now for iOS devices. Mostly with iMessage!
LED Flash for incoming calls and notifications for better accessibility
Custom vibration for incoming calls for better accessibility
VoiceOver improvements including custom element labeling
Custom tones for Calendar events
Custom tone for Received Mail
Custom tone for Sent mail
Custom tone for Voice-mail
Year view on Calendar: iPad only
Week view on Calendar: For iPhone & iPod
New Music App: Redesigned only for iPad
Music & Video: Two separate apps for iPhone (Instead of Video inside iPod app)
Scroll for long song titles
Song description: Tap & hold on a song title for description
Smart Playlists: Sync smart playlists from iTunes.
Weather Forecasts updates hourly
On-location Weather: Determines current location. Custom locations can be added/
Alternate routes in Maps
Print Maps: Print location, direction maps
Twitter Pictures: Use Twitter pictures for contacts with integrated Twitter
Auto Download in background: Newstand issues, apps can be downloaded in background once subscribed.
Sync in background: Now possible to use iOS device while it is still syncing in background
Links in background: Safari links, iTunes links can be opened in background
Space usage: Determine space used by each app, supported file types under settings
iCloud usage: Determine space used on iCloud under settings
Change device name: Change iOS device name on-the-go via settings
Some GUI Improvements
Personal Dictionary: Create & store own words for re-use
Built-in Dictionary: Built-in dictionary app
iTunes Tone Store: Choose, Buy, Install custom tones
Improved FaceTime video quality
VoiceOver Item Chooser
Speak Text:Speak text based on selection
Delete recent calls: Delete single or one-by-one recent call list
Delete app data: Delete saved games, saved data for specific apps / games
Time mid-call invitation alerts
Download Multiple Apps: Now its possible to download and install multiple apps instead of one-by-one.
Delete songs: Check to Delete songs / playlists on iOS device (It’s already possible I guess in 4.3.3 or its here on my phone only for me? )
New Keyboard Shortcuts: Type OMG and it will type Oh My God.
Custom Text Tones: Custom SMS tones. (Yeah, I think it’s there)
Auto Sync backup: It takes backup of the file on the device. Hence restoring from scratch is made easy. No need to grab all apps one-by-one. Saves lot of time.
‘Install’ link instead of Price if the app is already bought.
Silent Switch: Shows volume level along with the Bell icon while switching back from Silent to Ringer (Currently it shows only the Bell icon)
Hotmail accounts have new icons & folders
Sync events, contacts, notes with predefined accounts under Mail.app (Like Hotmail, Gmail etc)
Marked Apps: All apps that are downloaded on iOS device for your account are marked as FREE (Free to download if they’re & free to download because you’ve already purchased them)
Arabic language support for VoiceOver
Icon Badges: Option to turn ON or OFF icon badges for apps. (Red circle with update)
Accessible input for mobility
Assistive Touch Gestures: Allows us to use iPhone with adaptive accessories while controlling touch sensitivity.
FaceTime over 3G: Yes, it is now possible. Not yet available for developers though.
Unsecured call notifications: I am not sure why does this prompt for confirmation for calls saying network is not encrypted! (Is this a feature or incomplete program?)
Mid-call Invitation Alert: If the phone is busy, we can still receive a placed conference call (Description is my interpretation)
Free @me.com email address: Yes. With iCloud integration, all iOS 5 users will get @me.com email ID
Custom Gestures: Create and save custom gestures. Mainly for motor-disables persons for use with AssistiveTouch accessories
Swipe-Left can let you browse through day-view one-by-one in Calendar
FaceTime without Sim card: FaceTime can now be activated and used either via a phone number or email address (Apple ID)
Unknown Caller details: When received a call from number that is not on contacts – the display also shows city name associated with the area code. Currently it shows in recent calls list only (I think I have seen this feature before on 4.2.1. Did you? )
Vibrate Alert for sent & received emails (What is they come-and-go the same time? Confusing?)
Real-TIme stock updates
Multiple Mark Read: Can now select & mark multiple emails as read.
Pause Timer: It’s possible to pause the Timer instead of ‘Cancel’
New German Keyboard: Easy access to Germanic umlaut
1080p Playback support for iPad. (Awesome)
Social Networking Integration: Facebook, Flickr, LinkedIn, MySpace along with Twitter (Options under Settings.app but not sure if integrated throughout the OS like Twitter)
Headphone Balance: Option to choose Left & Right balance for headphones under Accessibility
Mono audio option for headphones under accessibility (except to choose balance as mentioned above)
Cellular Network for App Store: Option to Enable or Disable using Cellular Network (GPRS, 3G) to download apps from the App Store. (This is excellent!)
Disable In-App Purchase: Ability to completely disable In-App purchases
iTunes Password Prompt: It is now possible to set frequency for iTunes Password prompt to appear.
Storage Usage Clean Up: We can not only see what files have taken up the space but we can empty that space with single wipe like Apps, Game’s saved data, Music, Videos etc.
Equalizer Presets: These are now more BASS oriented (Most likely)
Improved Sound Check for music
RSA ID is now available when setting up VPN. (Thanks @jaytrixz for this update). This is for performing two-factor authentication for a user to a network resource.
Folders for Mail: Yes. Possible for any allowed mail account including new Hotmail. (I mentioned about Hotmail above but this is new feature for all accounts & thanks @Karl for this info)
Hide Keyboard: Hide (Dismiss) keyboard button whenever necessary. (This is for iPad only. Not for iPhone. Confirmed)
Find My iPhone: This is available as a part of iCloud integration with an option to disable it. (Thanks Michael for confirmation)
Scrolling Titles for YouTube videos
Double tap the home button on YouTube while watching a video to see who uploaded that video (Thanks @JohnothanVincentCrook for pointing it out)
HD YouTube video if connected to 3G
Option to disable HQ (HD) video playback over 3G
Take pictures using headphone remote: If you have headphone with remote them it is possible to take picture using Volume UP button. (Very useful if you have a tripod. Please confirm if anyone saw this!)
Animated GIF image support for iMessage. Does not animate in Photos.app
Hold and drag events from within different dates or time
Tapping and holding back button in Safari will show-up visited website history (iPad only)
Current time on Calendar if in landscape mode
New voices for Voice-Over
Option to display Stock & Weather widgets in Notification Center
Add family relations to contacts.
Restrictions with password required for purchases if enabled
Enable / Disable option for voice-dial if the phone is set to security with pass-code lock.
Purchase history on app store
Automatically set time for iPod Touches
Auto Correct & Spell Check are independent options.
Broadcast song information on devices (like car stereo) when connected over Bluetooth
New keyboard with prominent #(hash-tag) and @ (mention) buttons for Twitter app like we have a prominent ‘.com’ button for Safari address bar.
iPod app renamed to Music: How could I missed it writing here! It’s there on a screenshot on other post here
Enhanced Mail.app even in offline mode and sync back when online (like for deleted emails)
Help center: Learn more about every option under settings app to explore more about it (like Nokia has?)
New notification alerts within mail app if you forgot to write a subject line (Similar to Gmail!)
Hourly Weather Forecasts: Tap the current day and it will display hour-by-hour weather forecast. (This is separate from hourly weather update mentioned above)
En dash (–): Tap and hold hyphen (-) key to see & insert En dash. Em dash is already there. (Know more here about En & Em Dash)
Third-party Cables: Support for almost all third-party TV-out cables. No need to download Resupported from Cydia. This would be one of the major features if true. (Can someone without jailbroken iPhone confirm this?)
Choose Notification Type: Banner notifications or the classic pop-up notifications (for each app)
Mail Sidebar: Can be swiped in or out
Install Twitter from Settings app (Twitter integration as one feature each? see below points)
Tweet Location: in Maps
Tweet Picture: from the camera roll
Tweet Website URL: from Safari
Tweet Video: from YouTube
Backup homescreen layout on iCloud (Please confirm)
Backup app data on iCloud (Like game saves etc)
Backup purchased music, apps, and books on iCloud
Backup SMS and MMS
Backup ringtone(s)
Backup contacts
Schedule daily OTA (Over the air) iCloud backup
Message / iMessage: Repeat alerts up to 10 times
iOS crash reports to Apple with options: Send automatically or Don’t send.
Nuance Speech to Text: Not available in current beta but the most anticipated feature in final release. See concept here.(Speech Recognition)
Sync bookmarks, highlight from iBooks across devices
iMessages show a blue colored bubble to easily distinguish
Group messaging in iMessage
Delivery Reports
Read receipts for iMessage (enable from Settings)
See if other person is typing in iMessage (like in IMs)
Add Social Media info in to contacts
New rounded toggle switch
New separate Video app & icon
Nitro JavaScript speed improvements for Web Apps
iMessage will be sent as a text message in case iMessage is not available
Custom vibration for each contact so each pattern can let know who’s calling
New ‘Message’ option for iPod Touch under settings to use iMessage using an email ID
Setup AirPort device
Maximum recent email messages limit to 1000 instead of 200
Create & manage photo albums within Photos.app on device itself. (How did I miss this before? Thanks Joaquin for letting me know.)
(Custom) gesture-based lock-screen (Ability to define a custom gesture to unlock iPhone without need of a pass-code. This is not confirmed but rumored to be included in later releases of iOS 5. Do you see any benefit?)
Double tap the home button on lock screen to launch YouTube videos (Received an email about it. It was nice to have double tapping to play music. Why would they change? Someone please confirm if this is correct ) This is not correct. Instead it gives iPod controls and Take picture from camera options. Thanks JohnothanVincentCrook for confirming this.
SMS tones sound like they have been shortened than those were provided on iPhone 4 (Anyone felt it that way?)
While reading an email – swiping right would open a list of messages and swipe left would bring back to the open email message again. (Like if you’re reading an email from Inbox, it will take you to Inbox)
If you have multiple email accounts configured in Mail.app – swipe left or right from one’s mailboxes folder list, it will take you to another account’s mailboxes. (from Google Mail to Hotmail or back)
iTunes App: Support for match & find songs based on previous song purchases.
Free upgrade to 256 kbps bit-rate for purchased songs if backing up on iCloud
Support for multiple audio devices (Could not understand exact meaning of this)
Mirror iPhone 4 on Apple TV (Someone with Apple TV please confirm)
Skip tracks by swiping left – right on album art itself when not on lock screen (iPad only)
The name of the person that respond, appears in small light blue text directly above the response when SMS is sent to a group. (Thanks Melvin Baskin for emailing this)
Drag Keyboard on iPad: Drag keyboard up / down the screen wherever it is needed. It works for split keyboard as well.
(Source:http://techzoom.org/ios-5-complete-list-of-200-new-features/)