Jeff Alexander has posted on his blog about the new version of Windows Search appears to speed up not only searches (of course!), but Vista itself!
In his words: "Windows Search 4.0 was quietly released for free download for Windows Vista, Windows XP, Windows Server 2008 and Windows Server 2003. This one kind of came under the radar a bit so I thought I would give it a go and install. Well to my surprise my machine seems to be faster! And of course search is a whole lot faster."