Did you look to see how I sort by joined date and username? I build a link and use $_GET to pull out what I want to sort by when the query occurs. If I can make it so that it counts the posts of each user, and sorts it by that (check out how I count posts in my post count plugin) automatically, then I'm golden. The rest is just link building. It seems the first part of your post will be able to do what I need (although I haven't tested it yet) to get me to where all I have left is to link build. I didn't know you could make variables in the query, that's neat
A guy from the bbpress forums suggested I also make it so that the displayed number of users per page is able to be changes (like via a dropdown menu). That isn't hard, I think I'll do them both in a future release. I'm hoping they release .74 soon because I'll have to make them usable in that version anyway, might as well do the work then.