And the winner is... COPERNIC DESKTOP SEARCH

I've been playing around with the different desktop search tools since about Q2 2005. Google's was the first one I used, but was disappointed with V1 as I could not easily add network drives to the search. This was a pain, as I store a lot of data on network shares.

A friend tried to presuade me to use MSN's version, but I was on a "try an avoid Microsoft at all costs" episode, to I did a search on the net and stumbled across Copernic. I installed it and haven't looked back. The interface is neat and easy to use, and it has a little search bar on your taskbar, which is helpful for those "Where did I put that document?" moment!
I also love the preview pane, which allows you to view all the document types that are being searched!

I recently tried Google DS V3. I loved the sidebarm but the actual search functionality I found nowhere near as good as Copernic's. Sorry, Google, this is one product you're gonna have to really work on before you change my mind.