Pros:

- wonderful atmosphere and feeling
- clear and easy to follow instructions 
- great musical ambience 
- reasonable to plentiful amount of supplies (some levels were more generous than others)
- nice dark lighting effects
- cool custom radio voice-over acting 
- Metro 2033 fans will be delighted (especially with the third level) (works well with the Kalash mod made by  KoBRaAndrey)

Cons:

- first map, mall of Ukraine, I had some graphics lag, though it could be just due to my old graphics card. The other three maps were fine though, just the mall was laggy
- bot navigation on the third map was a bit wonky at times
- third map - bots seemed to get stuck at spawn, though a restart of the map fixed it. 
- finale: radio voice-over should be louder, I couldn't hear it very well the first time and had to re-play it again to hear (that and special infected + common kept interrupting it) 
- a bit horde heavy at the finale: I get it though that the C4 is supposed to make a big noise and attract them, but the instructions on the barrels were clear enough to make out the rest 
- kind of disappointed that the finale didn't actually have a typical escape vehicle per se, but what was really weird was that at the ending area - there was a closet door that was unbreakable - you could actually hide in there and you wouldn't get touch (perhaps it was a random glitch?) 

Conclusion:

Played version 1.1 (complete) 

Overall I really liked it. I did love the atmosphere that you presented in this campaign, though like others have stated, perhaps more of the surrounding area could have been explored. However that probably would have taken more than four maps and this campaign offered a pretty good mix of atmosphere and running (though more run heavy towards the end). Understandably it probably would have taken more than 4 maps to have gotten a full experience of running around Pripyat and the surrounding area, but it was great overall, maybe a bit short. Chapter titles sometimes didn't appear right away at the beginning of some levels, I thought my mouse had died, but didn't realize it was just a delay. 
Overall though, great campaign and a nice nod to Metro 2033 ^^. Perhaps even some nod to stalker series but I haven't fully played that series to be truly certain.