First of all, it's the best multiplayer experience of any non-MMO ever. You can gather all your friends into a party and switch from custom games to co-op campaign to matchmaking to Forge any time you want. Me and Wynn must have spent about two hours in Forge working on a single map, then were able to move to custom game mode to try it out, then back and forth to tweak it just right.
We adjusted one of the maps so that explosive barrels shot out from each base every 10 seconds into piles of more explosive barrels, grenades and Mongooses, then made the hill capture points in either of those places, so you'd have to move out of the hill point every 10 seconds or be killed. Of course, we didn't start out aiming to do that, it just kinda happened along the way. It's a lot of fun to watch everything blow up sky high... it's really like a fireworks show.