Pros:

crazily exciting hordes

real joy for those who love heavy firepower

some interesting "puzzles"

innovative design (e.g. the "Half-life style lift", the unsafe saferooms)

unique (comparing with other campaigns)

Cons:

the NPCs die or get hurt eaily and stupidly whenever they have to climb up or down long ladders

some "supernatural" design (e.g. the floating blocks)

some zombies suddenly appear in the air...

Conclusion:

It's a well-deigned, unique, exciting campaign. The hordes designs are good. For those who love heavy firepower plus intense killing, it's really an enjoyable campaign. I love it.