Pros:

-Very detailed
-Great designed
-Interesting panic events
-Fair difficulty (not too hard/not too easy)
-Easter egg just blew up my mind, amazing

Cons:

As for the campaign in general - none.
But: easter egg is not possible with bots...had to watch it on YT only. That's the only thing why I put 9.8 instead of 10.

Conclusion:

Absolutely perfect, must play.

Pros:

-Incredible level design, world feels really big and real
-Interesting places to explore
-Innovative panic events
-Voice actors

Cons:

-Didn't like the underground level that much
-Campaign was harder for me than others

Conclusion:

Everyone must play this, or you can miss one of the best campaigns ever made.

Pros:

-Details, design, graphics!
-Loads of places to explore, all of them are very interesting, and I'm pretty sure I missed something :)
-Large maps (personal preference)

Cons:

Absolutely none!

Conclusion:

Best (or at least in top-3) campaign for L4D2. Masterpiece. So much effort was put into this. The finale was very innovative and refreshing. Many people complaining about not enough infected, but for me it was ok since I'm not a pro player and I don't like when the game is hardcore. The amount of the infected is absolutely correct.

DOWNLOAD AND PLAY IT NOW!

Pros:

Everything is awesome in this campaign, I really enjoyed it from start to end! :)

Cons:

Well...I guess none.

Conclusion:

Great campaign with an exclusive layout setting, a must-play!

Pros:

 - Valve-quality (really great mapping work)
 - Nice events
 - Very long
 - AI nav is ok

Cons:

 - Way TOO hard in some places... I even wanted to quit the campaign. Finale was hard too.

Conclusion:

Really awesome campaign and must-play for skilled players. Other people can try it too, but do not expect walk in the park.