I upgraded to the L920 from an Arrive on Sprint and must admit that while I do, overall, like my phone, I am still kind of disappointed. With the exception of better hardware support, Windows Phone 8 doesn't actually improve on Windows Phone 7 in any significant way. There's still no notification center, the email client is still very frustrating, there's no separate volume controls, no backup for game saves, etc. It is also much less stable than Windows Phone 7, and some of the crashes are "catasrophic." I've had two 920s and both have had the "gears of death" force me to completely re-flash them. Battery life is also unpredictable: brilliant one day and atrocious the next, and I can't figure out why. And there is a serious problem with dust getting under the front facing camera and proximity sensor. The much-vaunted rear camera is great in low light, but for the other 90% of pictures you will probably take, it is actually pretty bad. In fact, I don't notice it being all that much better than the one in my Arrive in good light, and in really bright light, where any camera should take descent shots, my old Arrive's pictures actually look better. Recent attempts to fix these issues via new firmware have made improvements in some areas but made other issues much worse, and introduced significant connection problems. I hope Nokia/AT&T resolve these quickly, but you never know...
That said, it is a gorgeous piece of hardware and built like a tank. Overall, I definitely feel like I upgraded, but the upgrade was slight. Some of the major shortcomings are probably software that will get better with "Blue," but I think some of the issues are simply due to poor internals.
In short, I agree with some of the other posters: wait or go elsewhere.