Pros:

Style almost identical to Borderlands 2
Good character matching
High detail

Cons:

Handsome Jack's eyes are a bit too... big.
Height makes no sense, Zer0 is meant to be the tallest instead of Handsome Jack(apart from Brick, but he doesn't count here)

Conclusion:

I love this skin pack, it's amazing. I get the best of both worlds. High detail, simply beautiful. Looks like the artists in Borderlands 2 specially came to make these skins, they're really good.

I also support the idea of making Lilith, Roland, Mordecai and Brick for Left 4 Dead, I'd love to see it. Although if you were to do that, I'd love to see the newer version of Mordecai from BL2 than his older version in BL1.

Pros:

Beautifully designed
Wonderful setting
Highly detailed
Very difficult (This could be a con if you like easy maps, but I like a good challenge)
Hilarious ending
Tricky and challenging
Darkness of the lab breaks into light of the outside, very balanced
Creepy
Plenty of surprises (like 2 Tanks ._.)

Cons:

Easily lost
Gets even more difficult to play with bots
Too many special infected (I don't really like getting continuously pounced on)
If you don't turn on Game Instructions, you have no idea what to do next.

Conclusion:

It's a very wonderful map with plenty of surprises, both good and bad. But if you play this on Advanced or Expert, it's going to be REALLY difficult, almost impossible. I've already tried this on Advanced and it was Hell for me, so Expert will probably be impossible. I really love the ending, it's different and really funny and just brings back memories of Dead Center.

I was initially surprised to find that there were only 3 levels, but each was long and fun to play through. Would be nicer if there were 4 or 5 slightly shorter maps, than 3 incredibly long ones. I also personally think that the setting outside the lab (in daylight) would be better if it's split into 2 levels and a bit more elaborated on since I think that final level's a bit rushed (Then again it could be just me. I ran through the entire thing in a panic)

Overall, I really love this map. I love the concept, the texture, the detail, the shooting and the puzzles. Very good map.