Popular wisdom says you should wait for SP1 before switching to any new version of Windows. Ironically, the question on the minds of current Vista customers is whether it's the right time to switch to SP1.

Vista SP1 reportedly wraps some 551 bug fixes along with performance, reliability, and compatibility enhancements. But given how customers who have upgraded from XP have struggled with driver and application incompatibilities, it's no surprise that many are gun-shy of the latest update.

According to PC World's test lab gurus, the Service Pack is safe and it does improve performance, albeit not enough to crow about. My own, totally anecdotal survey reveals that some customers have upgraded with no problems (myself, for example), while others claim unexpected crashes and instability -- almost assuredly the result of driver issues -- but that any system speedup could just as easily be attributable to the placebo effect.

http://www.networkworld.com/news/2008/032108-vista-sp1-threat-or.html