One opinion here is that is doesn't contribute much if you have a reasonable amount of memory.

http://en.wikipedia.org/wiki/ReadyBoost

Though Kevin seems to be seeing a benefit.

Nick
>Why do you need a flash drive to get the performance? Can't it just use a portion of the hard drive?
>
>>I've been using Vista for about a month now, and (knock on wood) it's been great. (either that, or I've been extremely lucky).
>>
>>My new laptop has 2 GB of memory, but I recently learned of the ReadyBoost feature in Vista. I found a 2GB ReadyBoost flash drive at a local store for about $30, so I grabbed it. My laptop was pretty speedy before, but it's even faster now - I can actually tell the difference with the naked eye when I load several apps. So if you're a Vista user and don't mind giving up one of your ports, give it a try.
>>
>>Kevin