Forum Usergroups

When running a forum, do you stick with the default usergroups typically member, moderator, site admin, admin or do you create additional usergroups?

Assuming you do create additional usergroups (ex: New Member, Regular Member, Established Member, Trusted Member, etc.), what do you create, how many posts does it take to advance to a new usergroup and what type of perks do you offer for those climbing the usergroup ladder?