I really enjoyed the look and feel of these maps. They are impressive in size and detail and the story is well-written, even if predictable.
Here are some minor observations though:
1) The scenario doesn't seem to be balanced for Total Carnage, as there were many moments when I had completely ran out of ammo, I had to bump the difficulty down a notch to make it bearable.
2) There seem to be some minor visual glitches and issues in some parts, I don't know if it's because of the conversion or original bugs of the scenario itself. I haven't played with any plugins, and I used the OpenGL rendering.
Almost all of them seem to be present in Deep Doodoo, where certain walls display what Doom players refer to as a "halls of mirrors" effect, quoting the Doom wiki: "a shimmering mass is visible in the empty space outside, composed of parts of previous frames of animation".
The airlock that connects the normal and underwater sections also suffers from this, in fact it's acting in reverse from what I can tell, since the room gets flooded when the underwater section is closed and becomes breathing-friendly when the door leading to the flooded reservoir is open (which is both taller than the airlock and filled to the top with water).
Another issue for me was that during the first playthrough, I got softlocked on Aquae Perturbae. I think I grabbed an uplink chip earlier than the game would've wanted me to, because no matter what I did, I couldn't place it in one of the slots, no access hatch was opened and I couldn't progress, this was aggravated by the fact there's no spoiler guide available, so I kept wandering for about an hour before I loaded an earlier save and was able to finish the level. Aquae Perturbae also sometimes crashed the game, but it seems to have only happened when the level got bugged.
So both of these levels seem to have some issues. I haven't noticed anything else so far, but I just played it once, so it's possible I might miss some other bugs or glitches.
Edit: found one more bug, on The Gauntlet reloading the fusion pistol is broken, your ammo gets set to 1 shot after reloading.