I'll have to join the chorus of appreciation for The Green Herring, many thanks for doing all of the hard work!
Watching someone actually play my map was exciting and frustrating all at the same time. I keep second guessing myself, "is it too hard? Too easy? Not obvious? Too obvious?" and so forth.
I'm interested if anyone has played Map32 in co-op as well, since the map has co-op only areas and the even-numbered players are split up until they can find ways to mutate the level to find their buddies.
As for map 3, I'll go on record as saying I loved the abandoned/rusted base at the end, especially the fact that the first areas are devoid of monsters. I spent a long time contemplating that yellow door and wondering, "would it be awesome if there actually wasn't a yellow key and this thing is just here to add a sense of mystery?" Of course, then I found the yellow key, which I had apparently walked right past, and that idea disappeared with it. Nonetheless, the atmosphere of that end bit reminded me a lot of the Wrecked Ship from Super Metroid and that's always a good thing.