Updates to Left 4 Dead 2 have been released. The updates will be applied automatically when your Steam client is restarted. They will be coming arriving with an upcoming title update on the Xbox 360. The major changes include:

Left 4 Dead 2
Changed Survivorbot item hunting behavior
SurvivorBots now stay closer to human players in all game modes
Fixed Survivorbot navigation issue in The Passing: Riverbank
Fixed bug where a SurvivorBot could become catatonic when attempting to save another Survivor from a Smoker
Fixed condition where SurvivorBots would not enter the saferoom
Increased self-inflicted friendly fire damage from the Grenade Launcher
Fixed bug where the M60 would reset its ammo if dropped in certain situations
Car Alarms will now trigger anytime a Special Infected pushes/pulls/rams a Survivor into an alarm car. This change only affects game modes with human-controlled Zombies
Get the full article at store.steampowered.com