Good FUD-free article on Google Desktop.
Google Desktop is interesting to me because it really doesn't do anything new for Mac users. Spotlight indexes and finds my files, QuickSilver (or in my case LaunchBar) acts as an application launcher (and other things).
So Google either has their own strategic reasons for introducing GD or they think they can do things better. Probably both.
Unfortunately for me GD was plagued with a memory problem that would cause the GD Daemon to eat memory. I will be going back and trying GD when the next revision is made.