Pros:

Large map
Leaves
LOTR!!!
Sequels are fun
FUN
fun
FuN
Funn
It's fun
Plenty of supplies
TOWER!!
GAINT WALL
GATE!
FUN

Cons:

Hard alone

..yep

Conclusion:

Easily the best L4D survival map out of any other (default included)

Pros:

Big
Large

Cons:

A lot of frost in vision
Can't see more than 5 feet ahead
I felt cold
Invisible walls
Hard to navigate
Easy to get lost

Conclusion:

DATS IT.