It has been said that Microsoft rushed the development of Vista SP1 in order to help correct some of the stability and compatibility flaws that were keeping some large customers away from the relatively new OS. New reports from testers indicate that this rush might show itself in all new set of issues.
Here's what one tester had to say:
“Based on my informal tests conducted in the first hours of having Vista Service Pack 1 in hand, it's hard to draw any hard and fast conclusions. However, these mixed results do show some promise--and also show that your experience with SP1 may vary depending upon the system configuration. Our Test Center will perform further, and more in-depth, testing of Vista Service Pack 1 to determine to what degree Microsoft has succeeded in fixing some of the flaws and frustrations in its operating system.“