Well, I've got it. And holy crap, is it ever yellow.
Exec. Summ: A great upgrade from the Lumia 800. It looks fab. The screen's great. WP8 is a lovely, lovely OS. Nokia supply some great bits of software. Overall, very pleased.
In more detail: I've been using WP for about 18 months now and I'm pretty darned comfy in it. I like the integration of LI, FB and Twitter. I also think it has, hands down, the best OSK of any mobile OS. This was the first time I'd used WP8, though, and although it's not all that much different to WP7.5, it's still a healthy evolution-not-revolution upgrade.
Let's get one thing out of the way. This phone is massive; twig people need not apply. Well, I say "massive". I mean "a few dozen millimetres tall and wide, and weighs nearly as much as a bag of sweets".
Setup was a piece of piss. Microsim out of 800, into 920, and away we go. I signed in with my Microsoft account, and my email and contacts appeared. A brief sign-in to FB and LI brought up those bits, too. You get loads of goodies, too. Nokia Drive, City Lens, Smart Shoot, Panorama, MS Office, Music. There's more in the Store, too. There's a transit thing for people who have to use pubic transport, a creative studio for turning good photos into st ones, etc etc etc.
The screen. Blimey. For an LCD, it's brilliant. Blacks are pretty bloody black, and of course it's much crisper than the AMOLED display of the 800. Colours are much better, too - although if you don't care about colour fidelity and can live with a bit of fringing, AMOLEDs are still brighter and vividider. But that said, this is totes bright enough, and the viewing angle is super-wide.
Everything in this OS is smooth and slick, and that's something I value. It feels finished. I like that I can resize tiles on the Start screen. I especially like that I can go to Windowsphone.com, sign in, see my purchase history, and send apps to the phone. That saves a lot of faffing about.
I'm totally sold on the whole Windows Phone design and UI language; it works very well for me and is the best fit out of all the available offerings, so bear that in mind when you read my gushings.
I loved my 800 (which now feels like a phone for children, it's so tiny) and I'm pretty confident I'm going to love the 920.
(I still think the 800 is a cracking handset. Great screen, great size, great software. But I'm not going to miss the little door that hides the USB connector on the 800, not one bit)
ETA: The low-light abilities of the camera are under-, not over-stated on the web. It's surreal. More on this later.