So here was my scenario, using bbPress I had forums I wanted non-registered users to see and comment in, and some that only registered users could see and use. The problem was that there were a couple of forums that needed an extra level of hidden-ness for admin users (who weren't WP admins). This was exactly what I needed to add this functionality to the forums, and it was super simple to set up...although I was initially confused about assigning users to the groups, but this may have been because my forum admin profile didn't have the added forum group setting, and I expected the group assignments to show in a different menu (I haven't been using bbPress very long).
I also appreciated the setting to remove "Private:" from the forum titles.
Wonderful plug-in, highly recommend. Hope you can keep it updated.