A colleague just sent me a link to Exalead. It's just a search engine, but the user interface is pretty slick. Since it's the trendy thing to do now (rightfully so), they also have a desktop search solution coming as well. It will be interesting to see what they come up with.
In the meantime, I'm giving X1 another chance, playing around with their new beta. I can definitely appreciate the rich interface, but there are times when I also appreciate the simplicity and integration of Google Desktop Search. Wouldn't it be neat if Google Desktop exposed an API (web service or otherwise)?
Maybe Microsoft's solution will.
Compared to Google, X1 is a little better for use in the enterprise. Among other things, it allows you to configure indexing on remote shares - something that Google Desktop unfortunately lacks (I've tried using local mounts for remote shares to circumvent that, but that in turn caused other issues).
Then again, none of these solutions are particularly good for the enterprise - particularly in issues of document and file security.