The new software, which powers Apple's iPhone, iPad, and iPod Touch, comes after seven beta versions of the software, dating back to June when iOS 5 made its debut at Apple's Worldwide Developers Conference.
iOS 5, which is available as a free update, brings an overhaul to Apple's notifications system, alongside a new messaging platform called iMessage that lets iOS users text and chat with one another free of charge. The software is also deeply tied to Apple's iCloud service, which ferries photos, applications, and settings back and forth between iOS devices, and serves as a built-in backup solution. Perhaps most important of all, iOS 5 lets iOS devices stand on their own, removing some of the ties to Apple's iTunes by letting users update their software and edit media right on the device.
The new version of the software can be found by plugging your iOS device into iTunes. It's compatible with the iPhone 3GS, iPhone 4, iPhone 4S, third- and fourth-generation iPod Touches, and both the first- and second-generation iPad. Users with older iOS devices remain on older versions of the system software.
Below is the full change log:
iOS 5 Software Update
This update contains over 200 new features, including the following:
Notifications
Swipe from the top of any screen to view notifications in one place with Notification Center
New notifications appear briefly at the top of the screen
View notifications from lock screen
Slide the notification app icon to the right on the lock screen to go directly to the app
iMessage
Send and receive unlimited text, photo, and video messages with other iOS 5 users
Track messages with delivery and read receipts
Group messaging and secure encryption
Works over cellular network and Wi-Fi*
Newsstand
Automatically organizes magazine and newspaper subscriptions on Home Screen
Displays the cover of the latest issue
Background downloads of new issues
Reminders for managing to do lists
Syncs with iCloud, iCal and Outlook
Location-based reminders when you leave or arrive at a location for iPhone 4S and iPhone 4
Built-in support for Twitter
Sign-in once in Settings and tweet directly from Camera, Photos, Maps, Safari and YouTube
Add location to any tweet
View twitter profile pictures and usernames in Contacts
Camera improvements for devices with cameras
Double click the home button when device is asleep to bring up a camera shortcut on iPhone 4S, iPhone 4, iPhone 3GS and iPod touch (4th generation)
Volume Up button to take a picture
Optional grid lines to line up shots
Pinch to zoom in the preview screen
Swipe to camera roll from preview screen
Tap and hold to lock focus and exposure, iPad 2 and iPod touch (4th generation) only support exposure lock
Photo improvements for devices with cameras
Crop and rotate
Red eye removal
One tap enhance
Organize photos into albums
Mail improvements
Format text using bold, italic, or underlined fonts
Indentation control
Drag to rearrange names in address fields
Flag messages
Mass mark messages as flagged, read or unread
Customize mail alert sounds
S/MIME
Calendar improvements
Year view on iPad and new Week view for iPhone and iPod touch
Tap to create an event
View and add event attachments
Game Center improvements
Use personal photos for your Game Center account
Compare your overall achievement scores with your friends
Find new Game Center friends with friend recommendations and friends of friends
Discover new games with custom game recommendations
AirPlay Mirroring for iPad 2 and iPhone 4S
Multitasking Gestures for iPad
Use four or five fingers to pinch to the Home Screen
Swipe up to reveal the multitasking bar
Swipe left or right to switch between apps
On-device setup, activation and configuration with Setup Assistant
Software updates available over the air without tethering
iCloud support
iTunes in the Cloud
Photo Stream
Documents in the Cloud
Apps and Books automatic download and purchase history
Backup
Contacts, Calendar, and Mail
Find My iPhone
Redesigned Music app for iPad
Hourly weather forecast
Real-time stock quotes
Wireless sync to iTunes
Keyboard improvements
Split keyboard for iPad
Improved autocorrection accuracy
Improved Chinese and Japanese input
New Emoji keyboard
Personal dictionary for autocorrection
Optionally create keyboard short cuts for frequently used words
Accessibility improvements
Option to light LED flash on incoming calls and alerts for iPhone 4S and iPhone 4
Custom vibration patterns for incoming calls on iPhone
New interface for using iOS with mobility-impairment input devices
Option to speak a selection of text
Custom element labeling for VoiceOver
Exchange ActiveSync improvements
Wirelessly sync tasks
Mark messages as flagged, read or unread
Improved offline support
Save a new contact from a GAL service
More than 1,500 new developer APIs
Bug fixes
Products compatible with this software update: iPhone 4S, iPhone 4, iPhone 3GS, iPad 2, iPad, iPod touch (4th generation), iPod touch (3rd generation)
* Normal carrier data rates may apply. Messages will be sent as SMS when iMessage is unavailable, carrier messaging fees apply.
Source: http://news.cnet.com/8301-27076_3-20119307-248/apple-releases-ios-5/?tag=mncol;topImage