To say that this is a letdown is an understatement. The first player is called out by name by his fellow soldiers, can run, dodge, duck, look down the sights of his weapon, and is in total control of the game. This allows you to really feel immersed in the action. The second player is a nameless, faceless plus sign, simply there for the ride.
Co-Optimus gives the developers credit for adding in a co-op mode at all, but it seems like they did the bare minimum, just enough to be able to use co-op as a bullet point.