The texturing is the worst element of this map. Things are barely textured beyond a pave, and there is absolutely no light other than fully bright. Those need a lot of effort put into before they start working. Also, doors rarely work well in multiplayer, much less big ones that can easily be confused for a wall. Once you know they're doors, it comes natural, but until then, you'll be wandering around using up what little ammo and such is in that room looking for a way to get to the area in the screenshots... and probably not living. If those were just open all the way, all the time, you'd be in a much better position.
Nevertheless, for 2-3 players (4 would be too much, I think) I would assume Total Carnage to ensue. The small nature of the map means your chances of surviving the first few seconds are slim, but they are helped by the many 2x powerups around the map (along with the 3x powerups at the north and south ends of the map). So even if you get nailed in the rear with a SPNKr Rocket, you may just be able to nab that little yellow can of life just ahead of you.
All in all, an interesting concept, but it needs a lot more polish before you can consider it done.
Well, first off, I'd like to note that this is my first Multiplayer map, and the first map I've made that I'm willing to share. The Pfhortress on the Horizon is one of the maps that I'm currently making as a net pack, but I thought I'd release it early to get criticism. 4-players, 2 assault rifles, 2 smg's, 2 shotguns, 2 alien weapons, 2 fusion pistols, 1 launcher, and many health power ups. Enjoy the carnage, as you play in deathmatch, or every man for himself. (Please not, there will most likely be bugs. Please comment ANY issues you have, be it lighting, weapon placement, spawns, anything! I want it to be as good as I can get it! Any other feedback is also appreciated.)