Pros:

- Weapons, Ammo and Healing Items are very scarce
- Feels like a Real Survival
- Free roaming maps ; Exploring a lot
- Great Atmosphere
- Fun Puzzles
- Fog
- References to Silent Hill
- Long Campaign

Cons:

- Maybe more explorable buildings, but that would made the map too gigantic (it's already big) so it's ok
- Haven't found melee weapons

Conclusion:

It is a big file, something like 1+ gb uncompressed but totally worth it, make sure you get the sound fix, mute the in-game left 4 dead music and you totally sink in to the atmosphere, playing at night with friends with your lights off. It gives a new feeling to the gameplay, you start with a pistol only and 1 bottle of pain pills. Everything is scarce, the distances to travel are quite long, so it is a war of attrition with the special infected (since you find yourself brack tracking and exploring you don't find a lot of common, except for hordes). There are puzzles that aren't too hard to figure out but still pretty fun and the maps are a lot (I counted 11 on the select screen, haven't finished it yet). Overall this is a great experience, I recommend it to everyone just for the sake of trying something different, can't think of anything bad to say about this campaign.