In addition, Valve will introduce a series of weekly events dubbed 'mutations'; 20 have been planned for now.
Infected bots in versus, a new co-op challenge mode, a new zombie class, a golf club and an M60 will be the new features.
Now the bad news... as done previously with the original Left 4 Dead DLC 'Crash Course', the content will be free for PC users, while Xbox 360 gamers will have to pay 560 Microsoft Points.
This was highly criticized in its day and will probably gather unrest among the Xbox Live community, though Valve blamed Microsoft for charging the update in their system. Oh well, it'll probably be worth it anyway...