Pros:

-The thing works. 
-No noticeable nav problems.
-This is tough, Playing it a few times you can see the engine doing its work. One time one tank on the second map to second time the map delivering a special infected epic onslaught.
-unique maps and other new signs and textures.
-It’s long.
-Rewarded for exploring.
-Many spawn closets

Cons:

Some of the same glitichs as in L4D campaign but I’m not a programmer but nothing that makes it unplayable.

Seemed unfinished open areas in map 1 and others.

It’s just a BETA, not finished.

Conclusion:

My review is similar to my L4D review of the map.

Many improvement have been made sense version 2 and 3 of original L4D campaign. Little or no bugs.

One of the most complete campaigns made. With a final polish will take over the top.  I'm also rating as a BETA not finish. When complete this number could fall My rating is as high as it is because there are campaigns that are incomplete, broken, and missing textures with ratings in the 90’s if they can get that this deserves higher.

I hope the final will address open areas and play choices for better campaign. Also using more of the object and items available for L4D2.

Other note to some other the other comments I'm not punishing developer for the texture problems mentioned because of the tools and what builders have to work with.

Pros:

Unique interactions in the environment.
Looks Great.
Technical work is high.

Cons:

Every level is too long or large.
Pacing is bad on every level but last.
Unclear paths and direction.
Things in environment don’t make sense.

Conclusion:

First people are going to say why is the score low, I put a higher standard in a product that is Finished. There are lots of things wrong. Some texture errors or just strange. The pacing is terrible, problems with the level design. You will get lost because things are not marked or clear or just plain hidden. I do like long levels but this just too much.
 
Example:
On the 3rd level there is a misuse of the safe room marker not once but two times.
Path is obscured by a wall, then by three small boards that look like you could crouch to get through.  It took a bomb and several shotgun blasts to get through. A Bomb, could not take out three little boards! 
 
A lot the construction is in the realm of “this would be neat” but not logical in the real world. The story threats are strange, including the ending. 
 
It’s called Percent 84, it’s only in it for a blink. This looks and plays like very polished Beta. 

Pros:

-The thing works.
-No noticeable nav problems.
-This is tough, Playing it a few times you can see the engine doing its work. One time one tank on the second map to second time the map delivering a special infected epic on slot. 
-2-3 unique maps and other new signs and textures.
-It’s long.
-Rewarded for exploring. Yes you can get lost and as been mentioned by the builder signs are coming but if you look around on the 1st  and 3rd map there is extra ammo, guns, and grenades. So a plus over the Valve maps who seem to punish you for doing the same thing.

Cons:

Some glitichs but I’m not a programmer like the water effect being a little off zombies sometimes shooting off like a rocket into the wall after taking them down, and ending fly out models flicking out. But nothing that makes it unplayable.

It’s just a BETA, not finished.

Conclusion:

One of the most complete campaigns made. With a final polish should be one of thee top maps. If not now. My rating is as high as it is because there are map that are broken and missing textures with ratings in the 90’s if they can get that this deserves higher.

Other note to some other the other comments by posters. I don't get the comment about the vehicles. Have you been to CA Mexico border? Music would be nice :)