Steve, I use Traktor 100%..
My laptop that I use for gigs is still on XP, simply because I cannot afford to upgrade it yet but I will soon.
On my desk top at home that has vista on it and I run Traktor on it all day, editing, beat gridding, doing this, doing that........... you know all the stuff you can do with Traktor. I've had this computer for about 4 months and to date, not a problem, all is great (he says touching wood).
I find vista fantastic for editing and writing tags etc. to tracks, really good.
So, for me go for it, I will upgrade my laptop to vista when I get the funds together soon.