Co-op online was a mixed bag. While I had fun messing about in the open world with a friend, as well as coming up with different tactics to defeat the tougher bosses, the linear levels didn't feel like they were designed with co-op in mind. Firing your weapon and the hit being registered by an enemy had a noticeable delay. The most frequent bug was the game not registering the equipment that I wanted to switch to, which always seemed to happen in the middle of a firefight. The only resolution was to ask my friend to kill me to death, which he happily obliged. Thanks, Aaron.