My company recently purchased a google mini, our own little google search engine for our technical data and client information that is spread out all over between database entries, our samba file system, a wiki, mail server and other various locations.
It's slightly more powerful than google desktop search although probably with some hacking you could make gds just as capable if not more. The google mini is bolted down. You need to drill out the screws to get a peak at the type of hardware they use, and believe me I had the drill ready but my boss said "no".
It really isnt very configurable and leaves a lot to be desired in means of configuration and authentication. It currently only supports http://user:email@example.com type authentication internally or any type of IP based authentication you can set up server side which you could do for anything. That gave us a lot of problems with our wiki even though browsing the file system was easy using apache as a directory indexer with some simple authentication.
The worst part of the whole thing is that there is a liscensing limit to the number of objects it can index. you can only index 100,000 documents. That is nothing. I guess the google enterprise allows indexing of 500,000 but it costs 10x more.
All in all id stick with gds. It doest take that long to configure and run on everyones machines unless you have a large amount of people that need search access to a small amount of files.