This was a really fun map, especially lift drop to get the red key. It's short and action-packed, classic McGee design. There are a few technical/stylistic details I noticed, though:
+ The cage to the right of the blue key lift has a thin wall marked as an exit (line 166)
+ I'd move the start back a bit, so the monsters don't instantly see you. Id maps didn't start you in trouble without good reason. You could turn the monsters around, but that might echo Underhalls a little too strongly.
+ Move the killcloset walk trigger back behind the blue key elevator. As it is, you can trigger it just walking in front of the elevator, which seems like the wrong message, especially for a map02 - I accidentally hit it while dodging. You could alternately put it in front of the switch rather than the lift, which might be more interesting. You'd see the monsters below you, shoot, and get the demon charging after you on the same level (or chasing you from behind if you rush the key, a real race if you're low on ammo).
+ I see great potential for deathmatch here - a rocket in the red key area, a plasma near the blue key lift switch, and other weapons scattered about. I'm just waiting to see this - McGee maps were great for deathmatch, and you've nailed it with the layout.
+ The use of so many types of lighting doesn't really feel like McGee - usually he'd stick to one or two per level. Lamps plus side lights plus Tekgreen/metal lights seems like overkill
+ The transition from BrownGreen to TekGreen is sometimes abrupt (example: the starting location). McGee almost never did this without having a door or shifting the geometry
+ The tekgreen1 at the start of the blue key area (line 347) feels out of place for McGee
+ The health left in somewhat narrow open areas is more a Petersen trait.
Other than the extra exit and start, these are minor concerns - the map itself was great on first pass. I'll play through again as time permits and see if I can come up with anything else on repeat plays.