The new Windows 7 is what Vista should have been. As far as programs go, it should be retroactive with audition, but I'd recommend the new Audition 3 - better quality and effects.
Yes, I have had opportunities to use both. In my Vista experience, it took me 5 minutes to get the $%^# thing to lock up and require a reboot. 7, in contrast, seemed much more stable and less problematic.
However, I've been using Macs myself for some time, and I would never go back to Windows for multiple reasons which are beyond the scope of this thread.