Pros:

- incredible level design
- well thought out progression through maps
- very nice detailing, but...
- impressive technically (scripting, multiple paths, etc)

Cons:

- poor frame rates
- consistently too dark throughout campaign
- collision bug with helicopter wreckage
- zombies punch through bottom of finale plane
- bots occasionally get stuck
- usually not clear where to go or what to do

Conclusion:

The creators of this campaign obviously put a massive amount of work and attention into this project, it's just too bad they missed some fairly obvious and easy to fix problems. 

The level of detail is amazing, but if you're going to do that you need to put just as much work into optimizing the area as well. Also, the level of detail can't just be outrageous all the time because when everything has tons of stuff it all starts to look the same and you can't tell rooms and areas apart. Combined with the lack of lighting to indicate which direction to travel in--and lack of lighting in general--makes it consistently hard to find your way through the maps. It's kind of a shame that people with this much talent and experience at game content creation made what are typically newbie errors. The collision problems with the helicopter wreckage and the finale plane in particular are surprising, as those should have been very easy to catch during beta testing and also very easy to fix.

Hopefully they'll get this stuff figured out as this could be the greatest user created l4d content ever created.