Same texture on walls and floor (This usually only works for vents): http://imgur.com/RhSrEQ5
nav_build_ladder: http://imgur.com/5tiXVP8
The sky is black: http://imgur.com/VjAF4Hm
This wall could use some details: http://imgur.com/RvUUQ4O
LOD water is broken: http://imgur.com/yoMbT4Q
Cubemaps on some props is broken: http://imgur.com/ZPLlokH http://imgur.com/SuNx7WM
This ledge is too high for the player to cross it smoothly: http://imgur.com/Dil21PN
point_spotlight: http://imgur.com/0NKazXo
Stairs could use some playerclip: http://imgur.com/F2D3kQx
Func_detail uneven brushes: http://imgur.com/HkmNOyk
Floaters (Hard to translate without a radar): http://imgur.com/FiIOb9P http://imgur.com/HwHVQQS
The map is blocky, try adding pipes and add more textures to create depth.
Look here for examples