I like it a lot. That style has been done a lot but there's nothing wrong with that. I haven't played it yet but looked around and here's some suggestions and ideas:
1. PHONG SHADING. All those beautiful curves deserve nothing but the best. I'm assuming you're using arghrad already because of the sunlighting, so just go through and give the surfaces that make up a curve a light value but leave the "light" flag unchecked. Any touching surfaces with the same value set will be curve-shaded together.
2. Use _sun_surface instead of _sun_ambient. The problem with _sun_ambient is that any surface that has a line of sight to the sky is lit with the same brightness regardless of how little of the sky it can see or how far away it is. It's good for outdoor-only areas with lots of sky when you want a minimum light value, but for combination indoor/outdoor areas you get those secondary shadows. This is what's causing those ugly patches of light just inside hallways. The worst is when you go up the lift, then ahead and down the ladder, where the double stairway is. sun_surface will make the sky give off diffuse light instead and get rid of those secondary shadows down the halls.
3. The sunlighting is kinda garish and harsh. No big deal though. It looks like you're using a _sun_color of around 1.0 0.7 0.2. My choice would be something like 1.0 0.8 0.4. It's all cool though.
4. That area with the "island" and the megahealth and rocket launcher is a pretty big dead end down on the lower level. It stands out because it's the only major dead end in the entire map. What I'd do is, where the rocket launcher is, make a stairway down from there, turn right and lead to a small underground area, then out somewhere in the grassy area. Maybe to the right of where the red armor is, you could have steps up and out like a cellar entrance on the side of a house. You could also have a passage connect from the new underground area over to either where the ladder under the lift is or the room with the boxes and teleporter.
5. I'd recommend a fitting texture for the risers (vertical parts) of the stairs.
6. I'd also recommend using a variety of textures for the walls. It looks like there's about three "levels" of wall surface throughout the above-ground part. Maybe use the existing texture for the lowest level and maybe the top too, and a second texture for the middle level. This will break up monotony in the taller rooms.
7, It's kinda dark in the room w/boxes and teleporter. I think it's cool that way (for example it was a while before I saw the BGF) but others might complain.
Oh, BTW, the teleporter is badass, and the vent/jump-pad with the blue particles is especially badass. If I get a chance I'll give it run with bots later on. Right now there's a certain trilogy I need to look at...
I used Phong Shading *cries* It just had some issues I guess
Anyways, I'd rather not use any more textures then I really have too -- also, I'd like to defend the the Rocket Launcher area. If you go up the stairs to the GL, you can jump to the armor, and over to the place where the Shotgun is, I guess it's a kind of walkway.
Thanks for the tips on the lighting, I'll look into it