Pros:

Minecraft-based campaign.
Had to do some crafting to progress through some areas.
Great design.
Some surprising easter eggs (at least I think they were).
Couple of surprise appearances of Minecraft mobs.
Fun finale.
No noticeable bugs or glitches.
Bots were actually useful.
Minecraft Music, and dark cave noises at certain parts.

Cons:

It's not on L4D2!  (Won't take points away, though, hehe)
Other than that, none I can think of at this moment.

Conclusion:

Fantastic Minecraft-based campaign for L4D1.  What can be said, besides this was one of the best custom campaigns I have played on L4D1, and would definitely play it a quite a bit more.  If you're a Minecraft fan (or maybe not), would recommend anyone that owns L4D1 to check it out at least once.

Again, fantastic job, and great campaign.