Pros:

-Some of the best level design I've ever seen
-Excellent use of particle effects, ambient sounds, etc. The little things here are great
-The "fake finale" in map 2 was awesome
-Nav meshes are perfect. Not one issue
-Lighting was done extremely well and looked very realistic

Cons:

-I was often lost, especially in map 3
-A few areas seemed like they were using too many zombie populations

Conclusion:

Excellent campaign. Excellent design. It's hard to get any better than this. I just finished playing this and it's inspired me to make my maps better.