Pros:

That poster.
Custom melee weapons.
Intro is decent, better than most.
Custom music.
Great level design.
Atmosphere is believable.
Third level is amazing.

Cons:

I only got to the third level. (-0 points)
Noticeable lag on the starting point of the first map after the intro. (-0 points)
Backtracking was needed in some parts, but it wasn't that big of a deal. (-0 points)
Invisible specials and zombies in some parts. I disabled all campaigns and infected skins before doing this campaign. (-0.5 points)
Melee weapons don't have custom icons. (-0 points)
Runtime errors completely ruined the entire experience, as when I get one, even if I'm in the saferoom, I have to close and reopen Left 4 Dead 2. That poses a big problem if I'm doing in on solo, which I wasn't, but still. (-3 points)

Conclusion:

I have to admit, the campaign is amazing, but with all the problems I ran into, it's barely even enjoyable or playable. I couldn't even finish the damn thing. This hasn't happened with other custom campaigns before, even ones that featured new weapons or L4D1 characters.

I would love to give this the 9.5 or 10 it deserves, but it just can't due to the amount of troubles.