I played through this today, and I liked it up until map03, that's where it started to become fairly tedious, and it only got worse during the subsequent maps. HOWEVER I will break this review down into neat little packages wrapped all pretty-like.
VISUALS: I definitely enjoyed the atmosphere this wad creates: bleak, dark, and lonely. Reminds me of the time I died in a street at night back in 1934, some dude shot my ass dead I was pissed. Cool weird shapes and imposing architecture. I really didn't mind the oddly shaped teleporters, or the teleporter texture either, I thought they were decent and got the job done. The textures did get repetitive after a while but it didn't bother me that much.
MUSIC: Raw Ass. It was ok on Map01 and Map07, since Map01's song was decent and the map was short, and the shit was hitting the fan on Map07 so it was fitting. Besides that though it generally made me wanna IDMUS as soon as possible. Raw Ass. These maps would have greatly benefitted from moody, atmospheric songs.
GAMEPLAY: First the things I liked! I loved the amount of effort and thought you put into these layouts. They're very elaborate and expansive, with a stunning amount of secrets and different paths through a level. It adds a lot of replay value. You really nailed the feeling of exploring some large, dank ass abandoned bases. Ammo and health were generally pretty good, can't say I have any complaints in that department. Map07 was a pretty good Icon of Sin map. Now, unfortunately, the things I didn't like is quite a bit longer!
I was diggin' my time playing this during map01 and map02, towards the end of map03 however I started to feel "The Tedium", and "The Tedium" stems from multiple causes. First of all, gimme a weapon. Gimme a POWERFUL damn ass weapon, and pronto cause I got some pissed off demon nerds to kill before they slice my flesh to ribbons and make pulled pork sandwiches outta my ass. I got a rocket launcher fairly early on, but with limited rocket ammo I wasn't able to use it very often, so I had to rely on the ol boomstick and The Chaingun most of the time. Having to cut down hundreds upon hundreds of imps, demons, and especially cacodemons and hell knights with only those two weapons sucked, and I was pretty sick of it by map04. A super shotgun on map03 would have been a godsend. I eventually started MDKing higher health monsters like hellknights and cacodemons, and groaning like a dead goat whenever a horde of monsters would reveal itself.
Second of all, the monster selection was pretty limited, with only zombos, impos, daemons, hellknights and cacos making appearances. This made things pretty boring and predictable, with little variety. Now, this wouldn't be much of a problem if the maps were smaller, but these are BIG ASSED LEVELS that are highly complex in their layout and have monster counts hovering around 370. If this were a doom 1 wad that'd be understandable, but this being a wad for Doom 2 it felt like a missed opportunity.
Third, I felt like the fights were all very samey too, with only a select few battles standing out in my head. This made the limited monster variety problem even worse I think. I know you said you did this on purpose, preferring small free form skirmishes over scripted elaborate battles, but I feel like it made things too stale, especially given how large the levels are. By map05 and map06, I just started to speedrun the levels because I didn't want to shotgun hellknights and demons anymore. Overall it's a decent wad with cool visuals and a great atmosphere, and I can appreciate that you went for something a little different, but I think the resulting product didn't turn out so great gameplay-wise. Seems like it'd play better in coop or something, as playing it single player becomes extremely monotonous and plodding, for me anyway.