I haven't gotten far enough to unlock ghost yet, but I don't think i'd use it anyway. I'm a run n' gun, rush player. I love this game for this reason. I've run into plenty of campers, but with the wierd spawns and all, I can still defeat them. Just a bunch of little kids or losers who should try a different tactic with this game.
So far, I've had very little lag, but when it's there it is bad. I've even jumped out of the game a couple of times due to the laggy issue, but it's not near what MW3 was (is).