So... I finally got around to finishing this. Well, restarting it and playing all the way through on Hard this time. I dug out my old Dark Places setup so everything was "reel purdy" for the experience even!
Overall, it's a pretty pleasing episode. It doesn't exactly try anything new, but that's fine, as it almost feels like a collection of "lost levels" in a way. It's ripe with secrets, though none of them were particularly difficult to find. It has some fun triggered events that seem like a step up from what we saw way back in 1996. You could also see a difference in design philosophy with some of the larger, more open battle spaces that cropped up here and there. If I had one complaint, it's that the final level was pretty much a complete rehash of the original.
Maybe, just maybe this is Machine Game's way of telling Bethesda that they would like to give the Quake (ONE!) universe the same type of treatment they gave to Wolfenstein.