Your forgetting that the biggest new feature in Vista is that it's more secure. And yes, UAC is annoying for when you are installing the stuff for the first few days, but after, it doesn't bother you. And Linux has the same thing, unless you run as root (which makes linux just as secure as XP running as admin).
And yes, you can turn off superfetch. Go to start>services and then disable the service superfetch.
And btw, Voice recognition was not included in Windows XP, you either had to buy it from someone like Dragon, or get Office 2003. And Office 2003's voice recognition didn't work in other apps, life firefox or wlm.