An update to Left 4 Dead & Left 4 Dead 2 has been released. The updates will be applied automatically when your Steam client is restarted.

The major changes include:
L4D 360:
- Added "The Sacrifice" content.

L4D2 360:
- Added "The Sacrifice" content.
- Added "No Mercy" content.

- Game Play
• Bullets that first pass through an infected character before striking a Survivor are now ignored as friendly fire.
• Fix for survivors speaking The Passing Finale lines in other campaigns.
• Added a setup timer to Versus Survival
• Fixed bug in Versus-Survival where a team could get 5 survivors
• Removed Defibs and First Aid Kits in Realism Versus. Survivors start with a First Aid Kit, but all world spawns are disabled.
- UI
• Added vote option to enable All Talk in Versus.
• Added vote option to Restart Chapter in Versus.
• Added the ability in the lobby for all players to vote on starting the game.
- Versus
• Charger now receives 300 points for any Survivor that is insta-killed.
• Charger now receives 100 points for any Survivor that is insta-incapped by a charge.
• Any infected that causes a Survivor to stumble into a "ledge hang" situation will receive 50 points.
• Tanks go into a stasis when they spawn and leave stasis when the human player takes over.
• Tanks in stasis are invisible but still show a glow to the infected team.
• Tanks do not attack when they are in stasis.
• Tanks in stasis cannot be set on fire or damaged.


L4D PC:
- Fixed a few third person camera cheats.
- Added VPK audio cache support.
- Added "The Sacrifice" content.
- Added Versus Multi-Map Scoreboard
- Added the L4D2 Mounted .50 Cal
L4D2 PC/OS X:
- Game is fully playable on the Mac platform.
- Fixed a few third person camera cheats.
- Added "The Sacrifice" content.
- Added "No Mercy" content.
- Versus: Infected players will get a respawn time reduction against teams that rush.
- Removed need for Left 4 Dead 2 Add-on Support for Community Campaigns

More...