Pros:

really well made atmosphere
good details
interesting to play

Cons:

nothing i can think of right now

Conclusion:

I would really want to see some other scenes from the Matrix and maybe some more interesting effects.

Pros:

This campaign is one of the best. I played it in L4D and now in L4D2 is much better. 
I want to say that the last level is just perfect. I think it cant be better. All level are really good, but the last one is really well made.

Cons:

Not something so important. But i agree with doomplayer, it is a bit too easy. Its because there is ammo and good weapons at every 10 metres. This is the only thing i can think right now :)

Conclusion:

Amazing campaign, for sure it is one of the best. Really enjoyed playing it. Keep up the good work!