Updates to Left 4 Dead 2 have been released. The updates will be applied automatically when your Steam client is restarted. The major changes include:

Left 4 Dead 2

• New mutation: Chainsaw Massacre
• In Versus Special Infected bots spawn within 10 seconds of the Survivors leaving the safe room
• Shortened spawn times for human Special Infected when the Infected team isn’t full. The time difference is added to the timer of the next bot in line to spawn
• Exposed client

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Valve has now confirmed that "The Passing" will hit both Xbox 360 and PC on Thursday, April 22. As expected, the Xbox 360 download will be priced at 560 Microsoft Points / $7, while those playing on PC will get it for free.

The company also provided details on "Mutations," described as "a series of weekly game mode events" that " range from 'Realism Versus' mode to 'Chainsaw Massacre,' which gives all players chainsaws with an unlimited supply of gasoline."

SOURCE ...

December 14, 2009, 12:21 pm - Valve - Press Release

"The Passing" Brings L4D1 Survivors Down South

December 14, 2009 - Valve, creators of best-selling game franchises (such as Half-Life, Portal, Team Fortress, and Counter-Strike) and leading technologies (such as Steam and Source), today announced the first game add-on for its co-operative zombie thriller, Left 4 Dead 2 (L4D2), is in development and targeted for release ...