Just played some of it (died at the lab door that you hack) and must say it is a really good start.
The map has a good layout. I wouldn't change that at all. It does however need more detail still. Maybe some grunge and more wires. Also, in those longer hallways I would maybe use the bsp tool to cut or add in pillars along the sides. Or use a static mesh pillar to break up the normal straight 4-sided hallways.
The lighting needs work though. Majority of light fixtures I saw didn't have a corona on them, and the ones that did were way too bright. I think you should add coronas to all light fixtures that you want to appear as though they are giving off light. Also, the lighting seemed a little bit too bright. I would mess with radius and brightness to get nicer lighting. Maybe add some triggered lights as well.
Game play is at a good starting point. The first wave feels good, although after I hit the elevator button no zeds came at all and I feel like there should be a few. You also need to put some more ammo boxes in the map as well. I suggest testing the map on normal difficulty with 4-6 players and make sure that no one ever runs completely out of ammo. The lab door that I died at, while it was on solo mode, seems a little too hard with the amount of zeds that spawn.
I look forward to playing an updated version of this.