I am running Vista Home Premium with Pro Tools LE 7.4 CS5 and it works great. I haven't had any problems yet. And I can assure that in future versions of Pro Tools it will run fine also.
There really isn't any reason to switch to vista. In my opinion XP is still more stable with less bugs. Vista looks prettier, and has a few added security features, but that's about all... Use good security software with XP and you're set.