First let me say that regain is extremely cool. But I had a bit of trouble with the web interface and selecting resources, I don't know why, I could not browse my system using the selection button -- I had to configure the XML files by hand to make it work. I think there is a problem there.
Secondly, would be nice to have a small change to the tag library and an additional search.jsp so that one could output the result set as JSON or as XML. This way, the desktop search could be accessed via localhost using AJAX, and thus easily integrate regain results with other results.