Pros:

Beautiful, unique map design. Too be honest, it's one of my favorites. I feel like I am playing through a campaign that would fit in l4d. The final stage feels reminiscent of half life 2 which isn't a bad thing.
Legitimately challenging, it's not "easy" even on advanced. Though there were some areas with a lot of pills.
I actually liked the dark atmosphere, it gives the map a  grunge/horror feel that makes it more fun in my opinion. 

Cons:

The ending is the one flaw. The two tanks are very difficult to kill. However, this could have been because my group had one bot. I think if some pills were placed at the end it would be much more doable. 

Also, the colors change here quite it a bit. I'm mixed on this but it can be a bit annoying when you can't see very well. 

For the ending, I am not sure if you were going for humor or you just rushed the ending but it was pretty lame after such a great map. Either add a cool ending or make it more ridiculous.

There was one area, I believe the second to last stage, the tank was in the warehouse you have to open but for some reason he randomly dies. 

Conclusion:

This is a great and enjoyable map to play that feels like a real campaign because of it's high quality. The ending is extremely difficult so you might need either four people or to lower the settings. Whether you like the ending is up to personal preference but this campaign is still great so it deserves a high score. Best of luck!