Pros:

Tower Defence in L4d
vmfs for the mappers 

Cons:

bad nav
ugly map

Conclusion:

Absolutly love it! Great job on adding new gameplay to l4d. 
Since the map design is very... functional ... i hope that this is some sort of test for further maps/campaigns :)
Keep up the good work! 

Oh, and thanks for releasing the vmfs aswell. Very cool!

Pros:

Nice visuals
Good nav
In general very solid

Cons:

map 3 saferoom (bots didnt go inside, while constant horde)
map 4 a bit too much of maze structure
map 4 jockys everywhere!!! (i hate them :D)

Conclusion:

Played this in Singleplayer in normal difficulty and must say, that this is a very solid campaign. No showstopers/gamebrakers of any kind.
While i can understand that the standards for campaigns has been raised after playing ihm, dbd and so on, i still think people could appreciate the hard work that goes into making campaigns a bit more. Dont expect  Left 4 Dead 3 in every campaign you download. 
I would rate this an honest 80-85. Extrapoints due to weired community reviews

Pros:

realistic design
great weather effects and fog

Cons:

survival only

Conclusion:

solid leveldesign + awesome environment = Mustplay