Today saw the release of the first DLC for Left 4 dead. Features include the all new survival mode which pits the four survivors against an endless onslaught of infected. Each spawn has less of a lull in between and difficulty increases as time goes on. Eventually all four survivors die. There is also new leaderboards for the timed score of survival mode. Included in survival mode is the new lighthouse map from the (assumed) upcoming Last Stand campaign. Also released are the much anticipated versus mode of the Death Toll and Dead Air campaigns.