One interesting aspect of Vegas 2's co-op, and this is something that might upset some players, is that they've removed the ability to play with four players. Instead you're limited to having an extra member of the Rainbow Six team join up with your trio of soldiers. Essentially, the added player is left out of the core gameplay and can maneuver through the level however he or she sees fit. The host (player one) has control of the other two AI combatants and can tell them to do the traditional anti-terrorist things like moving to cover, breaching a door, and so on while your human buddy works on his own. I have to admit that it did feel a bit odd to be playing as the added player and not having the ability to command at least one of the AI -controlled Rainbow operatives (Why not give each human player control of an AI character?).