Great news from Cupertino, California: The wait is finally over. After nearly four months of extensive public testing, bug squashing, teeth gnashing and under-the-hood tweaking, Apple today released the final consumer version of iOS 5, a major and most ambitious upgrade to its mobile operating system yet.

Note: iOS 5 may not be available for some users yet as usually these things take a while to propagate thoughout all regional iTunes stores. iOS 5 is compatible with iPhone 3GS, iPhone 4 and iPhone 4S, third- and fourth-generation iPod touch, as well as both iPad 1 and iPad 2. However, some features are resource-intensive and thus only available on recent devices. Note that Siri, an intelligent personal assistant users can converse with, remains exclusive to iPhone 4S for the time being.

Preceding the iOS 5 roll out, Apple earlier this morning posted Find My Friends and AirPort Utility apps, enabled iCloud accounts for everyone, flipped the switch on the Newsstand Store and rolled out music re-downloading service dubbed iTunes in the Cloud in the U.K., Canada, Australia and other international markets. The iOS 5 software is available as a free firmware update in desktop iTunes. Just connect your device to a Mac or PC and follow the onscreen instructions in iTunes.

Due to iOS 5 installation being a major brain transplant, you’re strongly recommended to back up all your devices in iTunes before proceeding. In addition, you should copy your device backups and keep them safe, per instructions after the break. Also worth mentioning, the iTunes Terms and Conditions have been updated this morning, related to iTunes Match terms and collection of certain information from your iTunes library. The iTunes Match service is due for public consumption end of October. It is also rumored to go worldwide should Apple secure necessary licenses from record labels.

Now, onto iOS 5. As you know, iOS 5 has over 200 new features plus a handful of biggies.

Another big feature is the Notification Center which brings all those annoying notifications from app into a tidy panel accessed with a pull-down gesture. Twitter integration and support for other social accounts make sharing in iOS 5 more secure and uniform across apps. Other noteworthy goodies include wireless device sync with your computer or iCloud, all-new Reminders and Newsstand apps, new Camera features and a whole bunch of other improvements and little tweaks evident throughout the system. If you’re interested in everything iOS 5 has to offer, TiPb has a monster walkthrough.

Now, before you apply that firmware update…

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As a rule of thumb, you’re advised to perform a full backup of your iOS device in iTunes to restore to in case something goes wrong. Simply connect your device to a computer, launch iTunes 10.5, right click the device in the Devices pane and click the Back Up option.

After you’ve backed up all your iOS devices in iTunes, quit the program and perform a Time Machine backup of your system. Alternatively, copy the backup folder to a safe location, such as an external hard drive or a USB thumb drive. iTunes places the backup files in the following places:

Mac: ~/Library/Application Support/MobileSync/Backup/

Windows XP: \Documents and Settings(username)\Application Data\Apple Computer\MobileSync\Backup\

Windows Vista and Windows 7: \Users(username)\AppData\Roaming\Apple Computer\MobileSync\Backup\

We’d recommend starting from scratch and getting rid of your “old” app data, settings and other baggage which could degrade the experience. Setting your iPhone, iPod touch or iPad as a new device will especially make your life easier if you intend on cutting the cord and syncing with iCloud, iTunes be damned. Beware, though: Setting up a new device (as opposed to restoring from the latest backup) means losing all your text messages, missed calls list, device settings, as well as documents and settings from both built-in and third-party apps – literally, all data iTunes stores in a backup file each time you sync your device.

And here are your direct download links for the iOS 5 firmware:

• iPhone 3GS • iPhone 4 GSM • iPhone 4 CDMA • iPad • iPad 2 • iPad 2,2 • iPad 2,3 • iPod touch third-generation • iPod touch fourth-generation • Apple TV second-generation (iOS 4.4)