Right now 'Old Revisions' just shows the date of the revision - it would be nice if it also displayed the username of who made that revision (where available). As it is, you can sort of figure it out, manually matching up changes.log to the revision you're looking for, but it'd be nice to have it built-in. This is something I'm missing from MoinMoin (see:
http://moinmoin.wikiwikiweb.de/FrontPage?action=info - the arbitrary revision diff is nice too).