I'm one of those people. I switched to OS X somewhere around XP SP3. Have never used Vista on any of my own machines, and only run Win7 on a VM to get access to IE 8 and 9.
Search on Windows is horribly broken. One of the first "shortcuts" I learned on OS X was Cmd+Space and typing out the application I wanted to run. Spotlight immediately brought up what I wanted. Windows never did that for me, or spent 45 seconds or more with a spinning hourglass to return a document that happened to be named similar to a program I wanted. I don't care if it works better now, they've set a precedent in my mind that it is broken, because it was broken for the ~15 years I used their OSes.