I played this and found it enjoyable. There's some weird (shadow?) rendering issues in parts of the level, and holes in the terrain, but I'm sure you're already aware of this. I tried to jump on top of the wall thing across from that high up area with the extra ammo... but I couldn't do it. Not sure if it's possible, but I've always liked that sort of platforming challenge in FPS games. Also please add a murder room filled with enemies for testing purposes.
Pretty impressive for one of the few 3D agdg games!