We knew it was coming, but that doesn't make it any less exciting. Yes, that's right fanboys, iOS 5 is official - the first major update for Apple's mobile platform since iOS 4 landed back in April 2010.

And with it there are 1,500 new APIs and 200 new features; including 10 killer ones.

Taking a leaf from RIM's book - Apple has brought in iMessage; a new messaging service that works between all iOS users, regardless of what device you're using. It allows you to send texts, photos, videos, contacts, or even do group messaging with delivery receipts if you want.

It works on 3G and Wi-Fi, so you'll be able to use it out and about, and it's designed to work seamlessly across multiple devices so you won't end up reading the same messages twice. You'll even get a Skype-like notification that your iPal is typing away.

As widely expected the notifications setup has been massively overhauled. No longer will you be interrupted whilst trying to reach Island 9 on Tiny Wings, or be treated to a static lock screen or a messy homescreen with more red dots than a teenagers face - it's all neat and tidy, a lot more interactive and all very, well, Androidy (complete with a pull down bar at the top).

A simple drag right from your Notification Center, or indeed the lockscreen, takes you directly into the app. Nice.

One of the biggest advances in iOS 5 is that it is no longer tied to your PC by the holy white cable. It's a PC free experience, should you wish. Activating and updates are over-the-air (OTA) and you'll no longer need to download a whopping great file as all updates are just delta patches. A very welcome update indeed.

Newsstand adds a one stop shop for all your subscription magazine based apps, complete with background downloading of new issues.

Twitter is also on board iOS 5 in a big way, with deep integration. You'll be able to tweet from Safari, YouTube and the like and you can even instant tweet from your camera or photo roll. You won't need to keep signing in to Twitter either, you can save your log in details in your device's settings.

Safari has also been given a boost with a read-it-later function called Reading List that syncs across your Apple world, and, get this - tabbed browsing. It's like 2002 all over again.

Reminders is another nifty addition (and obvious glaring omission up until now) and also syncs across your iDevices (as well as Cal).

The Camera too has had a spring clean - it's quicker, there's a lockscreen shortcut button, a pinch-to-zoom option and you can do some editing from the camera app as well.

An iOS revamp just wouldn't be complete without a tinkering of the mail app though, and iOS 5 is no exception. It brings in rich-text formatting, indentation control, draggable addresses, easier flagging and the ability to search the entire contents of messages.

On a technical level there's now S/MIME mail support and a built-in dictionary that's actually a service across the entire platform. Thumby types (you know who you are) can also now split the keyboard into two, with a gap in the middle.

There's also AirPlay mirroring too and Wi-Fi syncing to iTunes if all the above wasn't enough for you.

It's out this fall, developers get a seed today for the SDK. It'll work on the iPhone 3GS, iPhone 4, iPad 1 and 2, as well as the iPod Touch (3rd gen or later).