In Vista, there are several options for giving your OS that little boost to get things running faster.  For example, if you are running Vista on a mobile PC client then you can take advantage of ReadyDrive to resume from Sleep faster.  Vista also introduces a feature called ReadyBoost which allows you to take advantage of a flash device to boost available RAM.  SuperFetch is another of the performance related features and allows Windows to prioritize commonly used applications in memory so that they can be accessed speedily.

It's also worth learning how the new power state called Sleep works in Vista because it's different on both Laptops and PC's.

Read about all of the Performance-related features of Vista here.