Windows 7 has greatly improved from Windows Vista.
However, it's still painfully slow on looking up files when your hard drive is full.
Microsoft tried to solve that with an indexing service, but that takes up a lot of resources, making response slower.
I also get the feeling that most of the improvements that are now in Windows 7, should have been implemented in Windows 98. I feel that a lot of Windows developers where anxious to get some of those improvements into earlier Windows versions, but where stopped due to Microsoft's bureaucracy.