I would wait at least 2 years after the release of Windows vista for most of the bugs, security holes and other problems to be resolved before upgrading.
I have Windows vista beta 2 (official Microsoft tester
), generally it's ok but has a long way to go.
If I was you lot, I'd go with Windows XP 64bit edition once the drivers catch up with it. Also SP3 is due out for Windows XP 32bit version and from what I've been told Windows XP 64bit edition will continue to get updates,patches for at least 2/3 more years.