Thanks for all the positive comments.

Nice to see that people are still having fun with this.
@Cali, I didn't make it with gameplay mods in mind so it probably won't play to well with them. In saying that, I didn't touch the stock weapons so it might be OK-ish (as it seems you found it). As far as the custom monsters go, I can't think of an easy way to deal with that. However, I'd say that many of them have pretty clear "if it wasn't this monster, which vanilla one would it be" alternatives so if anyone was desperate enough, they could spend a bit of time doing a find/replace in a map editor.
@GAA1992 I see what you mean about the start of the map. I've never played (or even seen) Disruptor before but there is certainly a similarity. All I was doing was trying to make the start area a bit like the one from the original Doom Legacy "Waterlab" but more interesting. That Disruptor game looks pretty interesting BTW. Looks like it's only on PS1 so I can't easily check it (although my original PS is somewhere and, as far as I know, still in working order).