A free update for the Xbox 360 version of Left 4 Dead is available now via Xbox Live. The update includes a host of fixes, tweaks and new features, including enhancements to Versus mode for improved competitive play. The full change list is:

General
Fixed Survivors being able to climb surfaces marked for versus infected only
Fixed a class of SurvivorBot bugs dealing with rescuing downed players
Players can no longer grab ladders while flying through the air after a Tank punch
Shooting near a car with an alarm that has already fired the alarm will no longer make chirping noises
Fixed mini-gun physics exploit
Fixed propane tanks (and other physics objects) causing players to fall through elevators
Fixed rare achievement bug issues
Fixed several map exploits

Versus Changes
Added HUD elements to show status of other infected players
Fixed instance where a Survivor changing to the infected team would be attacked by infected bots
Normalized special infected melee damage
Fixed exploit where infected players could run away and teleport back to gain health
Players can only change teams once per map
Players can't change teams while other players are still loading
Tank spawns at the same % through the map for both teams in versus mode
Made the Tank and Witch spawn directly on the escape route
Increased chance of getting the Tank or Witch
Fixed team swap issue

Hunter
Easier to pounce a Survivor who is meleeing
Increased Minimum damage a Hunter pounce does

Smoker
Fixed Smoker tongue tolerance
Smoker now has to be killed or the tongue destroyed for the tongue to break
Survivors cannot bash someone off the tongue until the Survivor being pulled is paralyzed or hanging
Tongue attacks that fail to paralyze or hang a Survivor will use the shorter ability delay timer
Fixed cases where the ability timer was not using the correct time
Fixed case where you could point at a Survivor but not register a tongue hit
Fixed Smoker tongue not targeting and landing properly through PZ ghosts
Smoker tongue does damage every second while dragging paralyzed Survivors

Tank
Bashable objects now appear with a red glow
Tanks hitting a car with an alarm disables the alarm permanently
Tank frustration timer is only reset by hitting Survivors with rocks or fists
Reduced autoshotgun damage against Tanks

Witch
Witch spawns at the same % through the map for both teams
Avoids spawning within a certain % of the tank
Fixed an exploit where the Witch could be woken up and tricked into attacking Survivors