Pros:

1) The maps are stunningly beautiful.
2) The spawning of special infected is frequent but manageable.
3) Events placement is good.
4) Excellent atmosphere.

Cons:

1) It could use a bit of music, honestly. In the second map, a 4-seconds clip is looping again and again and it's irritating.
2) Mediocre to Bad weapon / ammo placement.
3) Some models don't load and we see huge "error" signs.
4) It's easy to lose your path in the first map.
5) Most important of them all, it keeps crashing after the second safe room, from where you started. For example, if you start playing from the beginning, it crashes before map 3, if you play from the second map, it crashes before map 4. The left4dead2.exe stops working and you get thrown back to your desktop.

Conclusion:

OVERALL: An excellent campaign that is "infected" with a horrible disease and some other minor "flu-symptoms".
I highly suggest this map but be aware of its problems!