just played co-op for the first time and I really like it, there wasn't any lag and all the pick up items were shared. The only thing I didn't like was that I couldn't search ongoing games in any detail.
Spoiler
I think the single player DLC should let you play as Hicks when he gets woken from hypersleep just before alien 3 and explain just who the hell it was in his cryotube if it wasn't him, he said it was a long story so it is possible
I would also like to see some DLC set on fury 161 even if it's just multiplayer maps.