Pros:

_Nice Campain
_Nice Level
_Cool Design 
_FINALLY!!!!BOTS COME FOR THE ELEVATOR!!!AND IT WORKS! (I've did too much campain with elevator bugs...)
_Original
_The first time i was fearing in left 4 dead
_The last level futurist design is really cool.
_The desert...hell yeah.
_Strange ending but the animation is freaking cool.
_Long campain very long!
_The story you can follow on the walls are really cool, that's a good point!

Cons:

_Bots sometimes forget medipacks
_The ending is...WTF!?!? (you will see...you will see...)
_Long campain...very long! (yeah sometimes it's boring)

Conclusion:

This campain is for the moment the best I've played.
Only few little bugs to set and i can say that valve should put it OFFICIAL!
The story hid in the texts on walls are really cool, and the originality of the ending is amazing. (also weird like indian movies WTF...) 
and finally, elevators don't bug! Thanks God they Work!