Pros:

Nice long maps
Gorgeous visuals in many areas
Good difficulty balance
Good use of uncommon infected
Good placement/difficulty of crescendos
Fantastic finale
Interesting inclusion of NPC survivors
Enjoyable events, such as the falling vehicles, alarmed gun store, and "no weapons/ammo" setup

Cons:

Lackluster visuals in some areas
Some areas felt repetitious
(Non-melee) weapons/ammo scarce
Some AI navigation glitches

Conclusion:

A very enjoyable campaign with a good use of custom assets. The designers did a great job depicting the ravaged cityscape. I also appreciated the restraint practiced in the few modest crescendo events, avoiding an "as many as possible" approach. My biggest complaint was the inconsistent level design. Some areas are detailed, well thought-out, and beautifully designed. Others are uninspired and seem lazily put together. This felt especially egregious around the third time entering the sewer. In an unfortunate way, the museum in the finale is recreated so painstakingly that it makes apparent how bland many other areas are in comparison.