A comprehensive list of all the new features of iOS 5.0.-> SUPPORTS: iPhone 3GS, 4, iTouch 3G, 4G, iPad 1G & 2G.
-> Take camera pictures from lock screen
-> Enhanced notifications system
-> Auto backup to iTunes
-> Wireless iOS Software Updates "cut the cord"
-> AirPlay mirroring: Show entire iPad screen over AirPlay
-> iMessage app: competitor to BBM. Free messaging service over 3G and WiFi for all iPhone/iTouch customers
-> Enhanced Game Center; friends and achievement points
-> Rich Text Formatting for Mail app
-> Revamped iPad Music app
-> Pinch to zoom in Camera app
-> Pix editing in native camera app
-> iMessaging app- competitor to Blackberry Messenger. Completely free for iDevice customers
-> Emoticons built in
-> Over the air updates. No need for computer for updates... iDevice auto checks for updates and adds patches to device when available
-> Twitter integration. Can tweet Safari Links and get uptodate Tweet notifications and Tweet from within apps
-> Safari remniscent of Instapaper...
-> Tabbed browsing on screen (finally!)
-> Notification center; hub for all missed notifications and more
-> Instant access to NC by swiping down on top (similar to SBSettings activation)
-> Photostream, automatically uploads to iCloud account and allows for editing on Mac/PC
-> Newsstand – Newsstand will be your quick access to the Magazines and newspaper subscriptions on the iPhone and iPad
-> iTunes cloud support; buy once download automatically to all other devices on same iTunes account for free
-> iCloud, new file storage and sharing service, replacing MobileMe and FREE.....
-> Mail in all iCloud accounts kept up to date automatically
-> App Store, iBooks & iTunes all integrated into iCloud in similar manners. Buy once download for free on all your other devices
-> Enhanced and updated iPad music app
-> For the songs you've already bought, Apple has added a purchase button. Show you your entire purchase history. Look at it by recent songs or by artist.
-> 5GB free storage for mail, documents and backup. Not counting purchased music, apps, or books towards that. Nor counting Photo Stream.
-> Developer seed of iOS 5.0 released today, iCloud released today, dev build and Mac OS X Lion available for $29.99
-> iOS 5.0 Official release this fall
-> Ability to sync devices entirely via Wifi, iTunes cable or iTunes Match
-> What's iTunes Match? "It uses the fact that we've got 18 million songs in the iTunes music store. The chances are good we have the songs you've ripped. So we have software to scan your music and match it with the store. We give that music the same benefits as purchased music."
-> "iTunes Match will upgrade those songs to 256 kpbs AAC DRM-free"
-> "It costs $24.99 a year"
-> Lock screen shows all missed notifications
-> Sign in once on iDevice never need to sign out.
-> Facetime over 3G (?)
-> Panorama camera features (?)
According to: iOS version history - Wikipedia, the free encyclopedia
These are the changes for 5.0.1
Bug fixes, security update
Attempted to fix battery drain bug.
Fixes bugs affecting iCloud mail push.
Adds Multitasking Gestures for original iPad.
Resolves bugs with Documents in the Cloud.
Improves voice recognition for Australian users using dictation.
Contains security improvements.
Activates the LED camera flash, whether the speaker is muted or not, for incoming calls and messages, when activated within the Accessibility sub-menu.
Introduces a new way for developers to specify files that should not be backed up.
Attempts to fix 'Invalid Sim' and 'No SIM card installed' issues on the iPhone 4S.
These are the changes for 5.1
Initial release on iPad (3rd generation)
Enhanced Siri dictation support during text input "on supported devices" (iPhone 4S in 2011).
The Setup Assistant bug fix.
Carrier updates (e.g. AT&T 12.0).
AT&T indicator now says "4G" when applicable (HSPA+, iPhone 4S only).
Fixes iPhone 4S support for Caller ID Name Display (on supported carriers – i.e. Rogers & Fido in Canada).
Possible fix to Outgoing Call No Audio (OCNA) issue.
Turn On/Off 3G toggle button restored on iPhone 4S.
Combined Voice/Data Roaming Switch on iPhone.
Battery life reportedly fixed.
Bluetooth bug fix; enabling Bluetooth and returning to home screen, the Bluetooth icon still remains in the status bar.
Fixed Music coverflow slowdowns.
Shake-to-shuffle bug fix, which caused the Music app to freeze.
Smart playlists bug fix.
Genius now available with iTunes Match. Genius Mixes and Genius playlists for iTunes Match subscribers.
Photos can now be deleted from Photo Stream.
Safari, address bar added text (Go to this address); Bookmarks list no longer automatically displayed on browser opening, if last page opened before closing was blank.
Minor UI changes in Maps.
Japanese language support for Siri (availability may be limited during initial rollout).
Redesigned Camera app on iPad 2.
Add Permanent Camera icon that allows the user to start camera while the phone is locked.
Camera face detection now highlights all detected faces.
Improved Assistive Touch.
Improved Location Services.
License column added under the About menu.
App Store download limit over 3G increased from 20 to 50 MB.
Feel free to correct me with any wrong facts.