Pros:

- Very long campaign
- Puzzle sequences
- Upredictable
- Really unique feel
- Multiple endings
- Good atmosphere, quite akin to Silent Hill (or so I would assume)
- Varried levels, cramped indoors and spacious outdoors
- Supprisingly scary
- Well thought out event sequences
- Decent level design, scarcity of items encourages thinking outside the box and makes for a really tricky campaign.

Cons:

- Too long for a single sitting (final time was around a massive 6 or 7 hours), makes endings hard to achieve (?)
- Taxing to play but not difficult design-wise
- Occasional glitches with keys, requires suicide-restarts
- AI bots 'warp' around occasionally
- No friendly interaction / dialogue with bots, adding to atmosphere but making the mood artificial
- Areas too dark or hard to see in
- Very easy to get lost in exteriors, frustraiting to find out where to go in interiors
- Odd last puzzles, had to look up solutions (It's the limbs!)
- The dark ending' has some wierd draw distance issues, all actors can only be seen if they are right in front of you
- Credits roll is pretty abrupt, messy with the dead air logo

Conclusion:

I've never played Silent Hill game, but with this L4D mashup I felt like I had. The great recreation (from what I know) of the atmosphere, vibe, and world Silent Hill creates really makes this campaign show how much good effort the creators put into it. That said, the game it is for (being L4D), doesn't deal well with a lot of the ideas invested in the mod (see above), really breaking the traditional L4D feel. I enjoyed the campaign, maybe not enough to make it replayable, and would recommend it to anyone else still into Left 4 Dead.