Microsoft is trying its best to pull users towards Windows Vista. Even they have understood the fact that XP is way better and has more market share than Vista. Unofficially many tricks have been discovered for Windows Vista, but there was no official guide for customers by Microsoft.
Finally, Microsoft have released an official guide for tuning and tweaking performance on Vista. It focuses on common tweaks and performance improvements for single computer, as well as on tools used in enterprise environments.
The TweakGuides site has just released a free tweak guide for Windows Vista that includes various Vista tips, tricks and tweaks they have discovered till now.
This free e-book is a massive 250 page e-book that has everything from basics to advanced stuff and is definitely worth a read.