I purchased this mod and it's awesome!
Only problem is, when a user chooses from the secondary groups made available, the mod removes him from any other secondary groups he belonged to :-(
So lets say you allow your member to choose to join a Football, Racing, and Halo secondary group. When he chooses any or all of them, for some reason he is also removed from any other secondary groups he belongs to, like Moderator, Award Manager, Etc.
I'm not sure why the code does this, as you would think it would only toggle on or off the groups you select, but unfortunately when any exposed group is selected or deselected and saved, the user is removed from all other secondary groups :-(