The Heroic Map Pack has officially been released for Halo 3 and it was enough to drag TheFeed away from Call of Duty 4. Here's some footage of Foundry, the smallest map of the bunch.
In smaller games, this map definitely creates some cat-and-mouse situations and control of the rocket launcher and shotgun are going to be key.
The boxes and fences offer opportunities for skillful jumpers to get an advantage over less skilled players.
All in all, this is a great map.