Pros:

Very fun
Creative
Well laid out
Nav works perfectly
Perfectly executed weather/fog effects

Cons:

Few warehouse windows have no nav
Balcony stairs misaligned?

Conclusion:

I love this map!

Very impressive for a first L4D2 map, I'm guessing you've used other source games though? As the quality here is top-notch!

I should say that a few of the windows in the warehouse do not have nav linking through them, which seems odd as the player can cleanly get through, and there is no visible obstruction or reason to say why they shouldn't.

Also the stairs up to the balcony, although minor, the top 'rung' appears to hang in the air, the floor does not attach to it.

Aside from that, the map is incredibly well created, well done!