Felt a bit well oldschool like it was part of the MP2; more focus on exploration than combat challenge. Things like the optional SNG side area add to this.
The areas could have been a little more detailed to make them less samey-looking and easier for navigation. Combat feels mostly low-key, except for the exit fight which can turn sour if you're unlucky. Careful with spawn in such a room - the ruined bits look cool there, but the mid-high stuff creates ramps for the spawns to jump off from which can make them deal a ton of damage if they land on the player's head.
The roof/sky part is pretty sloppy construction-wise. And since it's all so open, it would have made for a nice opportunity to allow the player to climb up there at some point.
The wall fixtures for the torches are func_detail - better to make them func_detail_illusionary actually, so that one can't get stuck on them.
Too many torches for the vanilla protocol to handle, unfortunately.
A nice classic-feel map overall. Demo