I finally had the chance to play this map, and I think what you have here is a good start, but surely not a finished polished map. I think the layout is fine, but the button to start the horde was hard to find -at least for me it was.
All the steps in the map were much too large than they needed to be. the riser of the steps should be more about 8 units tall. Look for "simple_stairway_steps" in the "prefabs HL2" under the categories list for the entity tool for an example.
The buildings surrounding the space seemed to 'box-in' the level a bit too much. It came off as very closed-in. I would lower and vary the height of the roof lines for each of the buildings to get a much more natural feel to the landscape. Perhaps take the advantage of adding in a 3D skybox to give more perspective past the immediate walls.
I was able to get about 6 minutes on it before being consumed by the horde.
Overall, I liked the layout of the map. The rooftop is a nice touch, although that one room with the plank leading towards it, could probably use a door or something somewhere to suggest it could be connected to a larger building. As far as I can see it's only possible access (before the zombie outbreak) is through the 5 story window
But like I said, the layout I think is fine, and works really well. I especially like the placement for the knock-out wall and ceiling vents. It was fun to play, but pretty cramped and un-interesting in many places. It's a good beta release, but I think it needs a bit more detail.
