And there a lot of us who trust our moderators enough to let them ban and don't think that it's a "slippery slope" if it's done right, but we aren't exactly given many options, are we? Our mods can suspend members, but they can't change groups, guess how much of an effect that can have if you have components/applications that have user group based permissions, or if you want to set up an appeals forum for banned members.
I think you should let the admin decide how banning will be done on their board, keep the current way for those who want it, and for those who want their mods to be able to change user's groups add options so they can. That way your customers can run their forum the way they want rather than the way you seem to think that most of us want to run our boards.
I'm sorry, but those so-called banning system improvements in 3.0 were hardly improvements, and vB is still ahead of IPB when it comes to their banning system. I really hope that you make some real improvements to the banning system in 3.1, because 3.0 didn't improve much at all.
Really, all that's needed is simple, make it so the admin can choose to let mods ban, let admins set "banned groups" and users can be put there when banned by mods/admins and moved back to their old groups when unbanned. It's a little improvement but it's one that's desperately needed. Why is it needed? It's needed because some admins want to let their mods ban, some admins don't want to have to go to the ACP just to ban, some admins want to be able to choose the restrictions put on banned members, some admins have other applications/components and need an easy way to control their banned members permissions in, and the list goes on and on.