I personally would say stick with XP32 for another year or so. So far all
the DX10 talk seems to be more on the hype side than on the reality side.
Not that DX10 won't be the next great thing, but it seems it will be a
little longer than what some expected to be the next best thing. Plus with
all this DX 10.1 talk, I'm a little nervous about making the plunge on a
DX10 card. Maybe Chuck will give us a hint as to when we might see DX10.1 on
the street.
Here's an interesting article about DX10 games at the moment
http://www.twitchguru.com/2007/06/20/dissecting_dx10/
In regards to your question directly, nVdia support is alot better than 5
months ago, but it sounds like it might still be another month or two away
from being near XP's level. Since they are release 64bit drivers along side
the 32bit, I'd say the support is close to even.
So far, ever game I've tried to install under Vista64 as worked, to include
older ones like Quake2 and Warcraft 3. I have some other games like Blood,
Shadow Warrior and the likes, that I keep meaning to try.
Just a side thoughts, I have a AMD64 cpu as well, but if you're building a
new mid to high end system, I think you should be giving the Intel Core 2
Duo an eye, On July 22nd, they are cutting the price of their quad Core by
50%, which would have it priced around $230-250. All the Core 2 Duo Cpus are
64bit enabled as well. That or at least wait for the new AMD phenoms to come
out.
But if you're going make the 64bit plunge, I'd would go Vista64 or Xp64.