Pros:

Amazingly detailed environments.

Varied yet cohesive.

Funny easter egg.

Short storyline that does not impede the game flow.

Terrific ending.

Cons:

Huge file size, maybe that easter egg wasn't really worth doubling the file size.

(*) Edit: electrified water is still there as a random event, cool!
	

Conclusion:

Definitely one of the best custom campaign available for L4D2. Downloading this should be a no-brainer.