Typical server deployments will not get much from enabling SuperFetch, especially if you run disk defrag a decent amount, or use a 'in-the-background' defragment tool like Diskeeper. If you are using 2008 as a desktop operating system, it becomes more compelling.
By default, the Superfetch service is installed on a Server 2008 system but left disabled. If you try to enable it, the service won't start. This is easily fixed with 2 registry entries lifted from a Vista installation.
I follow your blog daily and want to thank you for putting this together. It is an invaluable resource. Do you plan on wrighting up getting the Hyper-V Intergration Services and drivers up and running on XP and Vista as I remember you mentioning Vista in an earlier post that it might be possible there too.
The required "stuff" underneath the Hyper-V layer isn't ready/there yet for XP. You can get the drivers to somewhat load but they don't have anything to hook into. I will be firing up a Vista VM sometime soon to try the IS pieces. I suspect they will work like they work for 2008 Server.