Pros:

-Fun concept
-Weapon Tech Tree and Building
-Nice small map
-Great intro & music
-Challenging 
-You build the escape vehicle
-Re-playable 

Cons:

-Machine guns and barricades inside are pretty useless
-Survivor bots are a bit useless

Conclusion:

A really well made build & defend map, more enjoyable with humans than bots, nice difficulty scaling and did I mention the escape vehicle is a rocket?