Pros: I gotta hand it to ya, this is a very original layout. I really like maps that are different. I like the different levels too, it mixes things up. Pretty good brush work also. Nice sky, matches the winter look you were going for.
Cons: I know you were going for that winter look and in a way you accomplished it. But I think if you could have mixed up the textures a little better. Example, screenshot 2 the textures are to close in color. Also the two metal boxes seem way out of place. Screenshot 1, the hand rail texture need to be aligned better. Looks like the rail has no top.
Improvements: A suggestion would be to make better use of the texture colors. Screenshot 3, if your a sniper, it would be hard to see which way the opponent might make his next move because the walls and floor all blend together. As far as the handrail, you could shorten the brush a bit or use the top button on your alignment tool. I see you only included 4 screen shots. Think about using all 6 available to show more areas of your map. Read some tuts on lighting on this site and look for light_environment.
If ya really want that winter look add some snow around. There are also props that have snow built right in.
Notes: I really like your map and you can tell you put a lot of effort into it. I'm really not trying to pick your map apart, I'm just pointing out some things that might be helpful. Very nice job. Well done.