What an incredible mapset, seriously good stuff.
I played through in 2 player coop with: the Naku-Naru weapons which I thought would match with the theme of the maps (they did very well), brutal doom monsters-only as I'm a bit tired of the vanilla roster's traditional moveset, and a resurrection/lives earned through monster kills system while refraining from saving and loading at any time during a level (only at starts).
We had an absolutely brilliant time splitting up throughout the non-linear levels and having to trek to each other to pop off a resurrection if we didn't have lives to spare. A demonstration: brother dies elsewhere in the map "Can you come get m--" switches to spectator view "Where are you at?!?" "I don't know lol" https://clips.twitch.tv/CleverAstuteSpiderKappa
We would constantly discover routes the other person had missed and it was like a giant game of show and tell, bringing them to the interesting secret or key location. Then the map would bring us back together as we ventured through the multi-key doors and switches, or where the level converged on a slaughterfest or boss. The pacing as you swapped between smaller maps and complex maps in addition to what seemed like a gradual increase in overall complexity throughout the episode was well done.
MAP07 Lost in the Forest - Gosh did I love trekking through the thick brush, getting ambushed, and later traveling overhead in sections you never even noticed! This one's my favorite!
MAP15 Mansion - We were both happy with the separate entrances we each were working through, only to later find there were a lot of ways you could approach this. Just really nice design.
MAP20 Ending - No explanation needed really.
MAP01 Mountain Pass
MAP03 The Farmlands
MAP04 River Valley
MAP05 Mountain Village
MAP06 The Secret City
MAP13 City Center
MAP08 Castle - What felt like maybe too much empty open space, felt a bit like generic slaughtermap, and then a slightly claustrophobic castle.
MAP10 Nightmare - The early sections felt a bit too simple and linear, but the back half with the dark corridors/bridges and the overhanging vines gave a really nice vibe.
MAP11 Nightfall - Hard to put my finger on it but it didn't seem to stand out much.
MAP12 Suburb - Much like Nightfall, didn't blow me away.
MAP19 Division - The beginning felt uninspired/boring, but the middle section gave us some nice Serious Sam vibes, and the final section was well done. A bit thematically disconnected overall.
Didn't really like
MAP16 Fort - Kinda boring.
MAP17 Prison - Felt too confined, samey looking throughout.
As a disclaimer, I guess I'll put it as someone else did, this is more of a relative ranking within the wad and all of the levels are really quite superior in the grand scheme of things. Looking forward to part 2!