Pros:

-Fantastic, creepy locations
-Superb Atmosphere
-Great Music
-Great Voice Acting
-Scary, unsettling moments
-Rain!
-Custom Tank
-Custom Melee Weapons
-The Voices.

Cons:

-Special infected are a little too numerous on the level where you retrieve the dog food.

Conclusion:

Me and a friend played this today. We agreed that it was by far one of the best campaigns for l4d2 we have ever played. It was obvious that lots of effort was put into making this campaign. And that shows in virtually every area.

I really liked the scares (I won't spoil them here.) My only possible complaint is the sheer number of special infected on the dog level, we had to re-do that one a couple times.