No, actually I meant acs-admin/users--under the "Complex Search" section where you can search for users in particular groups.
However, I also found another interesting thing--I created a new group type, and created a bunch of groups of that type. On the group admin screen it says "Display all 45 groups", but I don't have 45 groups, I have 19.
I've also discovered that the pl/sql function acs_groups.member_p is a no-op, it was never written. There does not seem to be any function defined in the system to tell me if a user is a member of a particular group.