http://e3.gamespot.com/video/6266199/?hd=1
When asked about the features in Reach, Joe Tung says,
There's a lot for people to get excited about. Obviously we've got the multiplayer stuff that people have seen in the Beta, best in breed matchmaking, et cetera. Screenshots, Theater, saved films, Forge, four-player co-op in Campaign. Obviously, an epic campaign. And then there's a bunch of other stuff that we're really excited to talk about in the coming months before launch.
"a bunch of other stuff" they haven't shown yet, other than multiplayer, Forge, theater, campaign and presumably Firefight since they're showing that at E3.
I'm long since out of adjectives, so I'll just say:
How?