Google Desktop - when I say "No" I mean !! NO !!
Google Desktop does have its benefits; I enjoy the email indexing, and the Adsense plug-in, and the slideshow - I've also tried out the Desktop SideBar but although it has its advantages ("Newsroom" being my favorite), the picture slideshow is buggy.
Both products - Google Desktop and the Desktop Sidebar - cause a performance hit - obvious slow downs and drive crunching. So, I tend to only run it for short periods of time.
DeskTop sidebar is nice and polite when I shut it down. It simply disappears. That cannot be said about Google Desktop. Every single time I shut Google Desktop down the same nag screen appears, and the tick box is always enabled.

Yes I *do* want to shut down Google Desktop, and I *do not* want it to start when my computer starts. For pity's sake just accept it and stop nagging.