Pros:

-Nice Envoriments
-Great Finale
-Fun Finale
-Reminded me a lot of Dawn of the Dead
-Only 3 maps, but still took about 54 minutes to complete on Normal.

Cons:

-The bots can get stuck around the place sometimes so I suggest you play this with as many real people as you can. 

Conclusion:

It's great, the overall length is great. I recomend that you try this out if you're a L4D2 fan.