Well, I haven't completed one yet, but I am maybe 2o turns away from it.
Playing with one friend.
Actually the game runs quite well in the beginnin, with standard size and 8 factions. But once you pass some time you start wondering about the incredibly low AI. We were playing on a small continent map and the AI was just unable to handle it. I was connected to an AI nation with just shore and they didn't come to me until about 1800 when they just planted a city on my island which I destroyed a few turns after that. Another Civ did the same, with the same result. War didn't mean anything, the AI was simply not able to handle it (Emperor). Besides, around the ages when you reach industrial the AI starts taking ages to process turns, which can take several minutes, becoming quite annoying.
Fights in Multiplayer versus other Players are handled quite horribly, clicking faster means victory. Especially annoying when your PC needs longer to load.
Well, I am not sure if I really want to get into the torture of that again after finishing this one game.