Apple's finalized the next version of its operating system, iOS 5, and it's a pretty big upgrade. Here's a look at all the new stuff you can expect when you install it on your iPhone, iPad, or iPod touch.

Notifications in iOS have always been obtrusive pop-ups and one of the biggest annoyances to users. Finally, in iOS 5, Apple's created Notification Center to solve that problem. Much like in Android, most notifications now pop up in the status bar. You can pull down the status bar to view any notifications you might have missed, see a little preview, and interact with them. You can still get notifications the old way if you'd like, and you can set what type of notifications you'll get in your system preferences.

In an attempt to untether your iDevice, Apple has created iCloud and iTunes Match. iCloud is basically a revamped MobileMe that syncs more types of data across your many devices as quickly as it can manage. (So far it looks like it actually works, too.) It doesn't just sync contacts and appointments, but photos and other media as well. This goes for pretty much any purchase you make through iTunes. Additionally, if you subscribe to iTunes Match (for $25/year for up to 20,000 songs), you get your music synced everywhere. You won't even need to upload songs already in the iTunes Store as Apple will see you have a copy of that song and allow you to download a copy from their store for free—even songs you ripped from a CD or acquired from other locations. If iTunes doesn't has the song, it'll send a copy to Apple and sync that copy with your devices manually. For $25 per year, it's a pretty decent deal. The only downside is you're always downloading a copy and you currently cannot stream your music from, say, a web browser.

Wi-Fi sync is a pretty awesome but also imperfect feature. It allows you to sync your device over Wi-Fi, just like you have it connected to iTunes. The downside is that you can't sync without connecting to power, so essentially you're still tethered to a cord. In a lot of ways this defeats the purpose, but if you plug in your iPhone in another room and want it to sync overnight it's still useful for that type of scenario.

Siri is a pretty killer feature in iOS 5 that Apple kept under wraps until the final weeks before its announcement. If you're familiar with Android's voice command features, Siri is a step above. Not only can it do things like control your phone, compose and send text messages, and play music in your library, but also look up information and perform complex calculations (via Wikipedia, Wolfram Alpha, and other sources) to help you find practically anything you're looking for. It works in the same fashion as its predecessor, Voice Control, by activating when you press and hold the home button. After that, all you have to do is speak and wait for Siri to obey your command. For more on how Siri works, here's adetailed description of its functionality and some of the many things you can say to it.

iMessage is essentially the exact same thing as the iPhone's SMS text messaging app, only it's now part of all iDevices. This means that iPhone, iPad, and iPod touch users can all communicate with each other via text message regardless of whether they have cellular service or not. It also means all your messages are push-synced to your other devices so you can pick up where you left off when you're juggling Apple products. For some this is very exciting, as it opens up the lines of communications further. Others find this unpleasantly reminiscent of Blackberry Messenger and are dreading the closed, Apple-only messaging service.

If you like the idea of reading magazines on your iDevice, you can subscribe to participating content providers and wind up with a fancy folder to hold your casual reading material. Newsstand is basically a means of creating quick little shortcuts to your digital issues rather than create an app to manage them separately. Strangely, Newsstand does actually run as an app and may make an appearance in your multitasking bar.

Reminder tries to remain simply by looking and acting like a to-do list. It's an Apple-made, mandatory app that lets you add a new task by typing it in on each line. You can set a date and an alert, much like you could with your calendar, and sync all your reminders via iTunes or iCloud. There's not much to this app, but if you've been missing a syncing to-do manager from Apple themselves, now you've got one.

It's always interesting to see which services Apple decides to integrate into their operating system, and it looks like this time Twitter made the cut. You can now save your Twitter login information in your iOS settings for direct integration with the official Twitter app (downloaded separately). This isn't hugely important in and of itself, but makes it possible for developers to have tighter Twitter integration. If you're a fan of the social network, third-party apps should start to get a little more appealing.

The Camera app on the iPhone is supposed to launch and operate a little bit faster, although it seems about the same from where we're standing. As for features, it now has an overlaid grid that you can use for composition. The real additions are found in the Photos app, which is becoming a little more like iPhoto. You can now edit your photos to reduce red eye, enhance, and crop.

Reader was a new feature that came to Safari in Mac OS X Lion, but now it's available for iOS. Clicking the Reader button next to any URL in Safari creates a more text-oriented version of any web page. You can then adjust the type to reduce eye strain, much like you would in an eBook reading app like Kindle or iBooks. If you're running iOS 5 on an iPad, you'll not only get Reader but another long-desired feature: tabbed browsing. It would be nice to have the option on the iPhone and iPod touch as well, but at least this is a start.

Mail has received some neat updates as well. Now you can style your messages with bold, italic, and underlined type by simply selecting it, tapping the more arrow, and choosing what you want to do. In addition to adding style, you can also look up a word in the dictionary and adjust the message quote indentation level.

On the iPhone and iPod touch, you can now view your calendar in a weekly view. On the iPad, you get a yearly view as well. In addition to these new display options, you can now add, rename, and delete calendars from your device as well.

If you have an iPad 2, or other iDevice with an A5 processor, you can utilize an awesome new feature called AirPlay Mirroring. This will let you mirror your device's screen on any AirPlay-compatible device (e.g. the Apple TV 2). This is great for demonstrations, but especially cool if you want to play a game (so we assume).

Apple has added a few new multitouch gestures for iPads. Using four or five fingers, you can now swipe up to access the multitasking bar, pinch inwards to return to the home screen, and swipe from side to side to switch between apps.