I was also burned by Vista, I got it at launch intending for it to replace XP (primarily for it's DX10 support). As I had 4Gb of memory I installed the 64-bit version. I struggled with it for about 2 months battling regular blue screens caused by the infamous nvlddmkm.sys before giving it up as a bad job. Up until 2 months ago I was still on XP but decided to make the switch to Windows 7. I'd already preordered a copy as it was being sold at a discount to U.K. residents for a limited time. My experience thus far with it has been an utter joy to be honest. Windows 7 is everything Vista should have been, i now have a fast, stable 64-bit O.S. with no complaints at all. The UAC is left on it's default setting and is a far far better implementation than the it's overly paranoid Vista brother. I've had no problems running any of the apps I used in XP. In short Microsoft have got it right, even if it did take just under another 3 years to do it. As -X- said if you aren't too sure, download the 90 day trial and see what you think. I'll admit that I was skeptical about Windows 7 at first, the old addage of once bitten twice shy hung over it, but I am happy to say it has so far proved itself in every way.
