I use Vista on my 5 PC's and XP on my laptop - no issues. They are all visible to each other and have no problem sharing files, printing to the shared printer, etc.

Recently I upgraded from Vista Ultimate 32 bit to 64 bit, and at the same time moved from individial HDD's to a raid 0 setup - the result was a significant improvement in performance. Very happy with the move so far.

Cheers,
S.