Pros:

Well made campaing. 
Wide scale maps.
Interesting events.
Exellent settings of boss and zombie spawns so as ammo.
Non linear ways to go.

Cons:

Multiple crushes in map 2 as client, no crushes as host. I think it depends of your computer and network speed in coop, because 1 and 2 maps are very large. (my system got 7.5 points Windows 7 system test)
Maybe add some mele weapons on map 3 and 4.
Some geo stuck in textures.

Conclusion:

Realy good and fun campaing. Requies some work and it will be exellent. I think need some graph optimization in large area maps.