Alright, try it out here:
http://cph01.collaboraid.net:8096/bug-tracker/bug?bug_number=1&reassign=1
Log in as "mailto:peter@collaboraid.biz";, password is "1".
One annoying thing that I couldn't find an easy solution for is that when you do the search, and then enter an integer, or the empty string, then that simply gets accepted as a user_id or unassigned.
Other than that, it works now, it's part of acs-templating, so everybody can use it, and you can even supply your own search query if you like.
Try it out!
/Lars
