iOS 8 has finally dropped. If you use a mobile device--an iPhone, iPad, or iPod--that's compatible with Apple's new operating system, you can now install the free update. There are two ways to upgrade: Directly from the device itself (Settings > General > Software Update), or by connecting the device to your computer and installing the update in iTunes.
The new OS isn't quite the overhaul that iOS 7 was, so it won't look radically different. But Apple packed plenty of new features under the hood: Continuity for working across all your Apple devices, home automation integration, a health app, third-party keyboards and QuickType, new photo editing tools, messaging features, and much, much more. (We have a full FAQ for you here.)
Then there are all the features Apple hasn't mentioned much but are definitely worth exploring, like a camera timer and an in case of emergency card.
Devices eligible to upgrade: iPhone 4s, iPhone 5, iPhone 5c, iPhone 5s, and the soon-to-be-released iPhone 6 and 6 Plus, which will ship with the new OS; fifth-generation iPods and later; and the iPad 2, third- and fourth-gen iPads, iPad Air, iPad mini, and iPad mini with Retina display.
You won't have to queue up online or wait in a physical line for iOS 8 like you had to for iPhone preorders last Friday or you will to buy a new phone this Friday, but there are still a few things you need to do to prep your devices for the upgrade. Chris Breen helpfully outlined the steps you should take (like backing up your data) before installing iOS 8, and also shows you how to downgrade if you hate the new OS.
We'll have plenty of tips, tricks, and how-tos up later today, so check back after you upgrade to find out how to get the most out of iOS 8--and let us know your first impressions.