Pros:

- Many easter eggs from the SH series
- Long campaign
- Challenging
- Puzzle elements that are quite unique
- 4 random endings
- Items that trigger events
- Levels design stay true from the SH series

Cons:

- Hard for casual players
- Darkness can be an annoyance in some areas
- Survivor bots mostly don't pick guns and med-kits 
- Survivor bots path-finding can be a mess, like  map 7
- CI and SI appear out of thin air
- No melee and no L4D2 weapons

Conclusion:

I played this campaign on single player in normal difficulty. All maps are actually doable, except some issues like getting all survivors into "that special room" in map 7, in which the player needs to " lightly push" the bots so they can get inside.
Map 11 is a really important map as the safehouses are generated randomly in which determine the ending that the player will get. So it needs to be played at least 4 times in order to get all the endings.
First time playthrough can be rough for most players as they need to take time solving the puzzles, otherwise it is a very fun campaign, especially for puzzle and SH fans. Great campaign made by the author and keep up the good work. :)