Pros:

-Custom models and textures everywhere
-Lots of atmosphere. Creative safe rooms and intro, huge vistas, very good drawdistance and very little distance fog.
-Performs well on my not-so-beastly computing machine, for its high-ish level of detail.
-Multiple paths that players will actually take
-Not really any bad gameplay created by the campaign itself, all the faults I run into are general faults of the game it was put in (boomer-bile + running event = borefest).
-Weapon and item placement makes sense.
-Not giving the godlike weapons until very late is a nice change of pace.
-There seem to be references to the L4D world all over the place (Help the victims of Pennsylvania? Is that what it sort-of says on the bus stop signs?)

Cons:

-Coach bot got stuck in the church door mechanism and we had to kill him.
-Very little dialogue, yet so much going on around the survivors.
-It's just TOO epic, dark, gritty, and real. Using the L4D2 survahvuhs here is like printing an epic poem in Comic Sans MS... is this why there's a distinct lack of them speaking?
-Boomer bile turns the running gauntlet events into sight seeing tours, way too many boomer biles for how much that item simply shuts-off the difficulty of the game.
-The soft-focus effect in the final safe room hurts me and my teammates' eyes.
-These are all MINOR complaints in an otherwise spectacular campaign.

Conclusion:

This campaign has heart, it has a lot of heart. It's all atmosphere, without much change in the gameplay at the later levels of the campaign, so it's still fun, but in the beginning levels you need to watch your ammo (which I got over pretty fast). Every scene is like a photograph, and there aren't any real negatives introduced in the gameplay.