Pros:

- Nice atmosphere
- Map 1's rainstorm literally made me want to look for a shelter in game.
- Did you use color correction on map 2? The feeling is very desolate. Well done
- The finale was gauntlet-type but not too easy nor too hard
- Not too hard to find out what way to go
- For some reason, there were no parts that bored me
- Items were pretty scarce and that's good. We needed campaigns where items weren't all over the place.
- I liked the decontamination shower tent. Nice addition.

Cons:

- The storms on map 1 were a little too frequent but I'm not sure that's something you control anyway
- The bots had difficulties here and there, but I don't take that into account since you should be playing this game with humans
- A little too short
- Minor detail: one area you see water dripping from the ceiling, but no water sound
- At the finale, it wasn't immediately clear where to go towards the end

Conclusion:

This is a very well done campaign. I recommend it to everyone. I haven't played it in VS so I don't know how that is, but in CoOp it's really good. Not too hard, not too easy yet very entertaining.
Solid campaign.