The Deskbar Applet isn't enough to write home about without Beagle. Beagle does the dirty work of fully indexing all your files so that search results are meaningful. As I suggested in my Deskbar Applet post, with these two together I've got a "good enough" replacement for the functionality of Google Desktop Search on Windows. Beagle is not fully functional for me yet. I still have to set it up or add plug-ins for OpenOffice files, PDF files, Gaim chats, and Thunderbird mail messages and attachments. I gather from some reading that the Thunderbird plug-in is far from perfect. And I would love to learn how to make it work like the animated demo where Beagle results are in the Deskbar drop-down, instead of only the entry "Search for xxxx using Beagle".
The best part? Beagle does enough of what I need to keep me content in Linux, and it is pretty.