nice
a) maybe put a ramp-like trim on the side of your stairs, so you dont have to risk losing your momentum by jumping on them?
b) doors to RA seem to open slowly. I always end up smacking into the wall resulting in a dead stop when approaching RA from that direction.
c) RA doors dont exactly look like doors

It took me two or three times to recognize that they were doors and that was an alternate route to RA.
To be honest, I like the RA area BETTER before I figured out about the doors

It made the path from MEGA to RA take a little longer (so you couldnt run both items as quickly) and made it a little more challenging to grab. Maybe try a version with those doors blocked off?
d) Most of your lights have a detail level of 10. This isnt necesarilly a bad thing, but it makes it hard for ppl like me (with lousy computers) to adjust lighting to make the game more playable.
Check out this thread:
http://www.doom3world.org/phpbb2/viewtopic.php?t=13335
It has become pretty standard for mappers making 'competetive' levels to set their ambient light on 10, and everything else lower. So when you type r_lightdetaillevel 10; only the ambient will be drawn, and the performance will be much smoother. Of course, whether or not you do this is up to you, but I guarantee some wanna-be 'pro' gamers will bitch about your map if you dont
e) There are a couple clipping issues:

I get caught up between these things

I get caught up on the corner

Again, caught up on the corner.
I dont think im missing any textures as the screenshots might suggest, Im using the same tex set for a different project and I think there may be some complications.
f) a lot of your ammo is located in corners.. it slows you down a bit when you need to snag something out of corners.
g) I LOVE the jump from the top down to the pillar, down to RA. Its very unique, I really havent seen a dropdown like this before. However, when I drop down to the pillar and jump to RA, unless I time it perfectly I tend to hit the wall above RA and fall to the ground. This is because the wall above RA sticks out farther than the ra platform. Maybe if you made the RA plat on equal length with the ceiling, it would be a more realistic jump.
h) The item placement is good as well, im just concerned that its a little too easy to jump from MEGA to RA. Also, Mega seems to be a more important item than RA in q4, so maybe switch ra and mega?
i) The ramps leading to the lowered foggy area that has large health are pretty steep.. maybe raise that area up a bit so you the ramps can be a little more even? I realise that the ramp to RA needs to be steep to make the jump, but the other areas dont need to be IMO.
Overall, the map is great

It looks good, the flow is good and with some tweaking it could be very promising!
GJ, as usual.