I have installed Google Desktop for four days now. The initial excitement has died down a little. The reality has started to set in: The thing is not going to work for me!
Why? Because I am organized. I have a meticulously crafted directory hierarchy based on the same principles that big research libraries use to organize their books. I have a habit of maintaining my files: putting them where they belong, deleting no longer needed files, archiving old files away, etc.
As a result, when I search for a word, say 'generics', most of the results are in my src/java/generics, src/c#/generics, doc/java/generics, and doc/c#/generics folders, all under my home directory. Of course, there are a few odd ball matches in other folders, e.g., temp/junk, but generally those are not what I want.
To really benefit from Google Desktop big time, you have to be really really disorganized: saving all your files in My Documents or the bin directory of the editor, saving all your email in Inbox, etc.
I've known a few people like that. They usually need help installing things themselves.
Google Desktop will be perfect for them, just as soon as I help them delete some old files, uninstall some old programs (including all of JDK 1.1.6, 1.2.1_05, 1.2.2, 1.3, 1.4.2_04, etc.) to make room for the Google Desktop index.