I tend to ONLY play the campaigns, as multiplayer has to compete with children, a mildly insane in-law, my wife, and the rest of real life (in that order)... and not generally with FPS games.
However, I have been able to clock some quick M/P time with AC:B, while said kids were entertained and the in-law watched on. Heck, the daughter was very helpful in piping up whenever something was amiss (sighted runner, another kill, etc.), and was supportive when I was invariably ambushed.
Now if they could just isolate mike chatter from other sounds, so I wouldn't have to dive for [MUTE] every time some dipsh*t with a very limited vocabulary joins in.