Many people on the net are complaining about Vista, problems with compatibility, uses too much system resources (Bloatware) and in a lot of cases is slower than XP. Indeed I recently bought a game called Crysis and the specification listed on the back for XP was a lower spec than that listed for Vista.
However if you remember XP, when it was initially launched, had the same problems both with people getting used to the new layout, incompatibility problems with peripherals that had been designed for use with 95/98 and the specification being higher to run the same game. So nothing new on that front. The advice at the time should be the same as the advice now ? if you don?t have to install it don?t until at least 1 year is up from launch and SP1 is out otherwise you are just a beta tester.