Yesterday I got to play the multiplayer demo for Halo Anniversary at Fan Expo. I got whooped, but I blame it on someone upping the sensitivity higher than I'm used to. We played a team slayer game in Beaver/Battle Creek, but I forget what they called it. It had a lot of changes like man cannons, expanded caves, ect. Everything looked awesome. It plays pretty much like Reach though, not that that's bad. All the menus looked the same, didn't get to peek in the armory though. The guy said "You can change your button preferences, but if you change your armour I will cry." He also looked down on inverting the right thumbstick, but that's how I play.
I'll try to get in to play again today, but I know the line will be much bigger. They gave out a code to the top two players of the round. I didn't catch what it was for. Early beta download I'm guessing.