I'm going to file this under 'wait and see'. NV's 8800 Vista (WHQL) drivers are definitely lacking, especially coming off of the XP 7-series drivers. However, I'm skeptical about ATI's drivers as well for the following reasons:
1) I just installed the Cat 7.1 driver + CCC for Vista (with an AIW X800XL) today, and while the drivers performed fine and the CCC is much zippier, the uninstall was ridiculous... It simply didn't remove the CCC, so it kept showing up when I'd reboot. Oddly, enough after I switched cards the CCC recognized that the video card was actually a GeForce 8800GTX! Long story short, I had to manually kill all the CCC processes (CCC.exe and MOM.exe) and manually delete the files in C:\ATI\. Not the most difficult thing to do, but it might not be as trivial a task for someone not very savvy. Besides, it's simply un-excusable that an app's own uninstaller can't find the app in its default location.
2) Seriously, can anyone remember the last solid ATI launch? All the high end X1800s and X1900s are great cards, but the X1800 launch was horrible and there weren't even decent XP drivers for the X1900s initially either. Look a bit further back to 2005, when both ATI and NV completely paper launched the hell out of X800 and the 6-series. Finally, Crossfire.... Well, that speaks for itself. The launch was horrible and lots of weaknesses were omitted in the pre-release PR.
3) If everything is going so smoothly, why is R600 launching almost 5 months after G80?
I'm seriously not trying to rip on ATI - they make great stuff... I'm just trying to put this into perspective based on history and my personal experiences with the latest Cats. Do I doubt ATI's ability to put out a sweet card and a great driver? no... I do however doubt their ability to do a smooth launch that includes great hardware; solid XP/Vista, DX9/10, 32-bit/64-bit, single card/Crossfire drivers; and availability of said hardware... There is just a lot going on right now, so It's only natural IMO that ATI (and NVIDIA) struggle a bit.
Hopefully, I'm wrong though, AMD will have been the best thing to happen to ATI, and they come out of the gate with R600 kicking and screaming. Chances are, I'll get one either way.
I just think that claiming victory for a card/driver that hasn't even seen the light of day is a bit pre-mature.