ok here come my picky suggestions
-Make the invisible wall you have uptop a visible wall. it will block out the bottom bland half of your sky from player view
-Make it slightly skinnier so you have some room from the ladder to possibly camp it from behind
-Add a metal bar or some kind of material in between each individual glass pane so it doesnt seem like you have random floating blocks of glass
-Add buyzones in case your map is ever used on a non gun game server
-Play with different glass textures for different parts of your map instead of using the same one throughout the whole thing
-Rethink your lighting scheme. With the sky you have your map is too lit up to be from natural light. Either add lights to your map or change your sky. For sky and suggested sky values check out this link:
http://developer.valvesoftware.com/wiki/Sky_Listit's starting to look promising keep it up =D. Oh yah I'll look more in depth into it later as to how to decrease the file size of your map didn't have much time right now