It's not like Mercenaries 2 wasn't looking good enough on its own. But hey, co-op never hurts, it only helps, especially when it's instituted in the way Pandemic have it running for Mercenaries 2. After you start, there's no game-interrupting menu screens, no lobbies, nothing. It's drop-in, drop-out combat, and while the guest's progress through the campaign won't be saved when they quit, they will get to keep any cash and weapons they pick up. As for the host, there's no adjustments made to the game when playing co-op, which means no extra enemies. So if you're stuck on a spot, no problems, just get a friend playing and you can hide your singleplayer shame amidst the high-fives and hollering.