I completely agree. I just played the co-op with a friend and it rocks. You HAVE to play as different roles in a team (medic, soldier, spec-ops). Thats the only way to survive the co-op. Its very different from the single player game which btw is FANTASTIC. I haven't even started regular multiplayer. This is like many many awesome games rolled into one!!
It is better to die on one's feet
then live on one's knees