Pros:

Amazing, beautiful, unbelivable, ultrarealistic maps!
I can just walking around and enjoy their beauty.
Quality of maps is awesome. I think they are better than original maps from Valve.
Some interresting events like fake esсape on the helicopter.
Many details, some of them are quite originally.
Really big spaces.

Cons:

Potential of the maps are not fully disclosed in my opinion, this means that maps are better than gameplay on them.
In some open spaces on some maps fps goes down, i think whole campaign must be optimised for better performance.

Conclusion:

Drop-dead campaign, i recomend it for all, but not for a weak PC. 
You exactly have not seen campaign like this before. ^_^