Pros:

-An actual example of how L4D2 CAN actually be a survival horror. Playing the second level on Advanced was about as hard as any other level in any other campaign on expert.
-Some of the creepiest infected models and some of the best weapon mods I've ever seen. Left me wishing I had some of the mods installed for permanent use. 
-Incredibly massive, sprawling levels left my final time on the campaign at 4 hours and 5 minutes, but never did I experience a dull moment.
-Level 2 in and of itself is a pro. If no other reason, play this campaign to experience the second level. By far the longest level of any campaign I have ever played, with the length practically quadrupled. And never, ever, does it get dull. The level keeps you moving through 4 environments that get progressively more terrifying.

Cons:

-City levels feel a bit padded out with a ton of houses that can't be entered, rendering them into nothing more than glorified cereal boxes with doors painted on them.
-The large open levels have a tendency to get confusing, and many times long roads that would, in normal campaigns, be assumed to be the proper way to go, instead came to a dead end.

Conclusion:

Despite the fact that I ended up putting a solid 4 hours and 5 minutes into it, this campaign never once lost my interest. Despite a part near the very end of the campaign where I had missed an item that was needed to progress, and wandering around in the woods or around the city trying to find the right way to go, the path of the campaign stays at least decently apparent. And the second level. I can not get over how incredibly well made it is. Indeed, every portion of this campaign shows an incredible amount of time and effort. To see how large each level is and that each of them still feels like it had generous amounts of time put into it is astonishing. 

For an overall incredible campaign, fantastic game play, and a pace that never really slows down for too long, 10/10, and then some. 

Pros:

-Strikingly incredible to look at. The map's remarkable level of detail reflects the amount of effort that was put into building it.
-Fits right in as a campaign that could have been released with the game. The levels are easy to follow but interesting enough that I spent several minutes searching around in all the areas that were off the main path.
-Simply fun to play, even for people (like myself) who have never had the privilege to actually play HL or HL2. 

Cons:

-Not so much of a con as just a point of interest. I left my Donkey Kong mod on for the tank, and so I would randomly encounter bananas or broken DK barrels where I assume there were supposed to be pieces of rubble. I assume the same thing happens if you leave a tank mod like Randy Savage on (except you'd see Slim Jims). So before playing, make sure to turn any tank mods off.
-My first play through on normal didn't seem to pose much of a challenge. Not that I was looking for or expecting this to be a challenge map, but those looking for a map that is challenging, this one will probably pose more of a challenge on expert, and even then with friends you'll probably be fine.

Conclusion:

The campaign is really and truly fun, despite being a little on the easy side even on normal difficulty. Never the less, this is a map that is worth the play.