Pros:

Adventure like
Map 3 has a really good mansion to play in and search
Intro is worth watching but not every playthrough
Custom servers (if you can find one hosting it) for variety
Looks like it took a long time to make...

Cons:

bland art/design in some areas
can't hear custom voices if you're blasting infected
Bots are brainless
big download

Conclusion:

Cold Case has immersion that's for sure. Has an environment that feels very horrific if you were to peek behind the scenes. I play the campaign every few months and its always interesting. Real people required and on custom servers. Solo is only fun on the middle levels, like within the butcher's mansion. Has bland level design in some areas. Other than that It's worth at least one play.

Pros:

*re-playable since strategies can differ
*unique upgrades not seen in other maps (props to the author for this extra variety)
*vehicles are badass
*has a 50's diner feel or back alley wrestling feel
*can summon classic survivors 
*very creative naming for objects
*instant death spot is hilarious

Cons:

*can't upgrade jimmy gibbs (or so I'm aware)
*the usual problems with 'Let's Build' concept (e.g. single player is hard, pushing 'e' a lot)
*instant death spot is frustrating
*SI get stuck a lot like behind ceda trailer

Conclusion:

Add some custom rock music or railroad tunes and this map would be killer.  Needs a motorcycle;  I don't know your modeling limitations or if this would add any value other than coolness.  Optimization has gotten better since the last build.  Worth playing with 3 or four real people.

Pros:

MR Newell in the flesh
random funny spottings
replaces DaC concert music

Cons:

gabe's nickname sounds fruity

Conclusion:

yes, get it. why not.

Pros:

Maintains the Half Life look and feel.

Custom music.

The train in the trainyard ran over Nick

Immersive

Cons:

Seven maps, though they go by quick

Big download

Nostalgia is required on the player

Average Finale

Conclusion:

Works as you'd expect, being able to run around city 17 with zombie fleshmen gnawing at your knee caps.  Re playable if you bump up the difficulty or play on Tank mode, other mutations, etc. for extra hilarity.

Pros:

Dark and scary for the newbie!
Hard puzzles will test your logical brain for once in l4d2!
Action packed.
Great start setting and fun finale with plenty of puzzles in-between.

Cons:

Near unplayable framerate on map 3 near the waterfall.
Still a beta but shows great concepts.
A bit too dark in areas (is this intended?) so keep that flashlight on.
More hints needed in map 4.

Conclusion:

If there ever was a physiological thriller within the l4d mythos this would be it.  Left4Dust surpases maps like silent hill to give players one hell of a time in l4d2.  A puzzle, fantasy map that you will want to play multiple times just relive the mind screw.  Most maps are huge with epic scale with dynamic areas. Note: requires at least 2-3 humans for completion.

Pros:

+Fun
+HAM !!!
+much detail
+great concept that could be added to any AAA game

Cons:

-more servers hosting please
-secret room has sub-par bot nav and you can get stuck easily
-safe closets needed probably before or near crescendos
-Spanish wall writings are not easy to read for a non-native speakers
-No intro

Conclusion:

I agree with everything collini_neut said.  Very fun so far! It may need more safe closets like right before crescendos (except for the finale of course which is good and hard). I've yet to get to the secret since i got downed and the bots are dumb in this area (i hope you know where i mean) so they never revived me.

Great job and my experience fit nicely since my survivors wore skins perfect for the fiesta. :D