Well there was a big thing in my school and town about how Master Chief takes off his helmet at the end. I think this is false though, I've beaten some of the levels on legendary either by myself, but it was much easier on coop, but duh. Anyway, the big changes are the very beginning intro movie, with only one noticable part, the one soldier kinda gets a little irate with the mouth talking about the covenant, but the ending was the same except for one thing, which i thought was pointless. Again like someone said, it's just bragging rights, knowing that you did it. Any big time special features, nope, sorry.