Ok, here are some things I noticed:

There's a slight performance drop around the middle parts. I see that you made some of the curved walls func_details to avoid them cutting into the ceilings? Maybe it's better to leave them as world brushes so they can act as a proper vis blocker instead.

I already mentioned how much I like the dark ceilings. Maybe you should get rid of and point lights and only rely on straight-down light_spots to keep the ceiling as dark as possible.

Add some smoothing groups manually and it could make the curvy brushwork look nicer. They are hidden in the texture properties.

I like this part so much. The architecture, the texturing... Only the ramps in and out this room could need some attention.

I like how well the bump mapping works on this structure, but it's also the place that makes me whish the map had at lease some basic theme or purpose. It looks like the shell of a rocket engine, but inside it's just a boring corridor. I don't know what to think about this. Maybe something simpler would be better. Something that would make more sense as a corridor.

I don't like the blueish and combine metal walls. I'd go for a rusty, industrial look for the whole level and skip the artificial, blueish combine textures.

The sterile glass walls, again, are a big theme break. I'd use a more basic elevator.

The colorful lights for indicating the 4 principal directions make sense as a gameplay device. But I can't help it, they're very ugly. Unfortunately I can't tell you a good replacement (textures, perhaps?). It's just that those red/blue/yellow/green lights look very killboxish :/

The wall has inconsistent texturing. Why not use the same texture like the side?

same as above!
I can see this map work very nicely. I don't like how physics props are, once again, hidden from the main parts (and likely to disappear in the water, soon). The jumppad works as badly as they did in HL1, but that might not be your fault. :wink:
I'd love to see a little more consistency in the texturing for the final version.
Good luck with this one!