Just wanted to post a few thoughts on this. Just quick observations really.
1) I've never really had difficulty not finding anything I wanted to find via the standard Windows Search, regardless of the operating system (I've used Windows 95, Windows 98 and now Windows XP at home, NT and 2000 at work). This isn't offering me anything better in that respect.
2) When I'm playing Games (not often these days, admittedly) I use a different log-in and close all other applications down. Most of the applications which start automatically (things like anti-virus software, firewall, soundcard settings) can be shut down from the status bar. If you right-click on the Google Desktop Search icon it opens a web page and doesn't offer any option to quit the program. To actually close Google Desktop Search it seems that you have to CTRL-ALT-DEL into Task Manager, then close the program from there.
3) My biggest issue with Google Desktop Search? Just out of habit I tend to password-protect all my Word documents. Google Desktop Search makes that just about pointless, as password-protected files are hidden from the search, and a preview of the file can be seen in the results page!
Normally I'm a fan of what Google do, especially the growing Docs & Spreadsheets web interface. However Google Desktop Search doesn't really do anything for me. Just the opposite in fact. What I really need to do with it is to uninstall it.