I have never had Vista x64 give me an issue. EVER.but overall pretty stable, not like Windows..
I see this thread becoming a platform war pretty soon so I'll comment before it does.
I didn't have any issues with my iPad until yesterday. Froze up when I tried to get in the iPod app and had GoodReader crash several times when trying to play a video I downloaded. Other than that no issues and a quick restart fixes the problem.