Pros:

- Far terrain landscape on skyboxes - great effect of roads and hills on horizon
- MUSIC
-Fantastic spooky atmosphere unique to this campaign
-Great events
-Dear Esther beach on last map?!
-Great attention to details
-Chapel illluminated by fires
-Mysterious idea behind underground tunnels
-Commercial quality design which can be seen everywhere. 

Cons:

-Tunnels are too long, clean, sterile and empty. They need more detail - something similar to floor in 149's finale?
-No CI, SI and tanks after picking up keys in finale?
-Finale to short after long maps full of detail and atmosphere, it makes me think "thats all? too bad". Something like Detour Ahead ending whould fit much better in terms of length

Conclusion:

Great campaign crafted with professional and commercial attention to detail which resulted in mature and uniqe atmospere. "Must play" for every L4D2 fan, same as One 4 Nine.