Pros:

* Nice atmosphere
* Nice setting
* Nice level-design
* Nice layout
* Nice gameplay
* Nicely detailed

Cons:

* Not much, maybe a lack of originality
* Last time I played it, the finale was really crappy, too easy!

Conclusion:

One of the best custom campaigns on Left 4 Dead 1 so far. It really blends with the other campaigns and has this creepy feeling that most of No Mercy has.