Everyone covered the main things I had... assuming the clipping you mentioned is getting caught on the fall down...
Woulda liked to see something on top of the roof of the room on the top floor with the hole in it... it exposes you to get up there so an adequate weapon reward is probably in keeping (or perhaps some contacts).
I'd toss a really lite light_environment in the map, with an intensity of like 5 or something... just enough to keep the areas outside from being ink-black (as outside never really is - even at its darkest).
I really liked the shape of the corridors down at the bottom of the cliff, it's an overused texture set and you went and made it feel fresh. Very good job on that.
One final note, I'd lose the skybox. Looking down is kinda dumb looking. Look for a skybox that incorporates a fade in color as you look down, so that the bottom face of the skybox is nearly black itself (I know you're not working with a cityscape, but the popular London skybox does this beautifully - just to describe what I mean, don't actually use that one). I think Crinity has some nice looking skies you could look into...
Oh, and path your zip (I think I wanna write a tut on this topic)
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