Unfortunately, if you're playing on an Xbox 360, choosing to jump in multiplayer games takes a concerted effort since all of the matchmaking is handled via a third disc accompanying the two-disc campaign. You can't start off with Disc 3 in the tray however. All of the navigation has to first be initiated from Disc 1, so that's at least one swap needed to play with or against friends. If you happen to be on the second disc of the solo affair and get an invite, choosing to accept it forces you to put in Disc 1, then 3. So, if you tally it up, in this scenario, you would have to change the discs in and out of the tray four times to play a game with a friend. That's dedicationand unwelcomed exercise.