I just struggled with this as my piece of crap Leadtek 6800GT just died on me. I needed to make a quick decision to get my computer up and running. I went with a 7900 GS from eVGA and so far so good. Delivers better performance than what I had in every category (which wasn't too bad till it died for no reason) and seems to have good support. I was tempted by the 8800 series, but I figure I'll upgrade more than my vid card when it comes time to dive into Vista (need to get new MB, dual-core, etc). And I'm happy to wait till they find out what's wrong with vista before I blow the cash.
My usage is general computer stuff, and I play WoW with pretty much all settings maxed on the new card, if that helps. So far so good.
Cheers
K
(sig is kinda off, sry)