I'm loving google desktop.
Here is my "google desktop" wish list in no special order. It might do some of these things for all I know, but there isn't much UI or documentation that might show me how.
- Ability to restrict search by file type.
- Integration with gmail.
- Tool to allow developers to write plug-ins to do something special with other file types.
- Syntax and/or configuration to include/exclude files or directories.
- Make initial indexing a little less intrusive re: system resources.
- Ability to search by other criteria.
- Ability to understand exif data, to allow for the searching of photos.

I just installed this after reading your post. I was amazed at some of the results it came up with! I like your idea about exif data. Perhaps a script could loop through all the pictures, extract the exif data and make shortcuts with the exif data. Crap. Now I'm going to be thinking about how to do this.
To add to your wishlist, I wish there was a way to look in other email programs besides Outlook.
The one-time indexing isn't going very fast on my machine.
Also,