Windows Phone 8 is more than just a new version of Microsoft's phone operating system that fixes irritations and adds missing features to catch up with iOS and Android - although it does that very effectively, and without losing the charm and individuality of the interface.
Multitasking is improved and apps now resume quickly, whether you use the Back button to switch back or open the app again from the Start screen.
It's crammed with more useful features and improvements than we can easily cover here and it comes on excellent new handsets from HTC, Nokia and Samsung at launch.
It's more than just a showcase for Microsoft services like SkyDrive and Skype and Xbox Music, although Windows Phone gives you a better experience with these than most other mobile devices.
Under the covers, this is key technology from desktop Windows running on a phone, and if you had any doubts about whether Windows could slim down to a lean, battery-friendly phone system and still deliver plenty of power you can set them aside.
This basically takes the training wheels off Windows Phone as far as developers are concerned, and means they can deliver the same powerful apps as any other smartphone.
But that doesn't make Windows Phone 8 complicated. Yes, it's powerful but it's also stylish and fun to use.
This is a delightful, elegant, enticing smartphone OS with a great browser and the best default touch keyboard bar none – and yes, maps that actually work.
Building Lenses into the camera app means you're more likely to remember to use the tools you've installed when you pull out the phone to take a picture.
Live tiles keep you up to date and in touch and the integration of social networks just keeps getting better now that Skype and other apps can put their contacts in the People hub.
And if you want to use your phone as a babysitter, you don't have to worry about the little darlings deleting things thanks to Kids Corner.
The Wallet is only going to be useful when your bank and your mobile operator catch up with the new technology, although isn't necessarily a hindrance.
Xbox Music will tempt you with music you can't listen to unless you're prepared to shell out for the streaming subscription (although it's a good deal) - we'd love to have seen the same idea with lenses used in the music hub to allow the likes of Spotify to compete on a usability level.
Until some more navigation apps show up or Nokia Drive becomes more widely available, only Nokia users get true turn-by-turn driving directions - and it's still light years behind Android's Google Maps in terms of functionality and ease of use.
Internet Explorer might be fast in some respects, but it's not the most consistent browser out there, and the UI still leaves a lot to be desired when compared to the more elegant options on the top Android options and iOS.
And existing Windows Phone users can't get this new version without a new handset, which is actually a big problem when trying to proliferate a new OS.
There's also the issue of media still being a locked down experience - we're impressed with the new media management tools on offer to get music and movies on the devices, but it's still a relatively limited file selection and lacks the speed and openness Android offers in this area.
Having a strong lineup of new features and improvements makes it hard to pick out any one killer feature you have to have, but the laundry list of all the ways Windows Phone 8 catches up with (and in some cases passes) iOS and Android misses the point of Windows Phone.
What Microsoft has managed is to bring all of this together in a seamless, elegant and engaging whole – and there's no longer anything missing to put you off.
If there is a single killer feature here, it's the Skype integration (or your other favourite VoIP app). Incoming and outgoing Skype calls work just like regular phone calls, except they don't use up your call minutes.
That said, it's still got a few more steps to make all of its offerings as rich to use as the competition, which is understandable considering it launched years later.
The application store is growing and has some decent titles (especially with the new apps launching specifically for Windows Phone 8, from Audible to Angry Birds Star Wars), but for sheer volume it can't compete with Android or iOS and you should check for specific apps that you need.
In short, Windows Phone 8 deserves its place as the third ecosystem in the smartphone arena, and provides more than enough to make it a viable alternative to the usual suspects.
For the first time user it's an excellent entry point into smartphones, with ease of use and deep contact integration fundamental to the experience.
If you're already familiar with Android and iOS you need to get used to a new way of working to get the most from Windows Phone, from using the 'Panorama view' in apps (which will either delight you as an easy way to see everything at once or confuse you if you forget to swipe and miss information) to pinning live tiles and following links to see related information like directions and traffic for a location or Facebook photos and Twitter updates for the friend who just texted you.
Some people find the interface elegant, others see it as stark. You might find the lack of a central notification area confusing, or you might prefer to see that information on the live tiles you choose to pin to the Start screen.
In short, anyone thinking of moving from iOS or Android to Windows Phone 8 will perhaps have to be prepared to make many adjustments - but there's no denying this is a real step up in quality from Microsoft and gives us hope for variety in the smartphone wars.