I believe it was tomshardware.com that did a complete analysis of both XP and Vista a few days ago to compare the performance of both OSes. The result was that Vista tanked on gaming performane, mainly because the graphics drivers and even the games themselves have not been optimized for Vista. However, audio/video encoding, file compression, and other multimedia-related tasks completed faster under Vista, some considerably moreso than others. Thus, it will seem faster in some areas and slower in others, but overall it will average out to about what you have now. Just keep up with any updates for your various software and hardware as updates should be forthcoming, improving the Vista experience.
I have just purchased a new Dell, which comes with an express upgrade to Vista. I've read that it'll take 6 - 8 weeks, but never mind that for now. I'm running an AMD Athlon 64 X2 Dual Core 4200+ CPU (2.2GHz) with 1 GB of RAM and a 128 MB video card on XP Media Center Edition. If I upgrade to Vista will I experience a noticeable performance change with my system? I'm more concerned about a negative effect since I'm guessing there probably wouldn't be a positive effect on the performance. Any information would be helpful.