Pros:

Very good game. Nice layout and textures.
It seems that the coop problem has been fixed. A friend can now join in the game at least in L4D2. I did not try the L4D1.

Cons:

Bots wont pick up first aid kits nor the pain pills.
This game coiuld not be played by a single player. Catacombs is not passable for only one human.

Conclusion:

The bots needs to be fix. It is difficult to pass this game without the full health of the bots.  The catacombs should also be fix to be played by a single player.