Episode 1 is just too easy. I appreciate that it's "cool" that map 1 is a retread of one of the last levels of Eviternity 1 but its far too drawn out and boring. Still likethe overall environment theme, which is the last episode of Eviternity 1 but made dreary with dark and hellish skies and all.
Episode 2 I *LOVE* the theme of the outdoors levels, which give off an Aztec vibe. I'm almost tempted to replay map 7 just because of the visual aesthetic (also a pretty good final fight). The outdoors levels also tend to let you kind of go anywhere and do things in any order you want. The indoors levels, unfortunately, aren't that interesting visually and are way too dark. Map 6 is a bit annoying with ammo starvation.
Episode 3 I *LOVE* the outdoors theme again. Map 11 is "Titan", so I guess its supposed to be a semi-terraformed colony there. It's uniquely kind of alien but still very earthlike, and you can tell that it's not natural but a place intentionally built to be beautiful and for colonists to live in. Map 11 also has great gameplay right from the start, I love maps which give an interesting twist like this where you start off with just a rocket launcher and have to do a bunch of work to get your other weapons. Most maps in this wad would be way more palatable to replay if they started off with a banger rather than ending with it. Map 12 is another pretty good one, slightly less beautiful but lots of path options, not too long, and the final fight is a pretty cool spectacle. Map 13 is meh, a lot less beautiful and more dreary looking, nothing too interesting. Map 14 is way too long and has... puzzles. Puzzles that are cool to see that you can do in Doom but not at all interesting to actually complete, even if they only take a few minutes apiece. Map 15 is also a bit dreary and not too interesting aside from the introduction of the veilimp which is quite the letdown when you realize how easy they are to fight.
Episode 4 I'm kind of ambivalent about. It's got a sort of... medievel village theme? Not very interesting. A lot of long drawn out levels without a ton happening for most of your time. Map 20 introduces the green hell knights and has a pretty cool final battle that uses a lot of the new enemies, which is quite a rarity in this wad.
Episode 5 I'm heavily biased against because I really hate the snow theme. It just doesn't feel right for doom, with hellish enemies throwing fireball and all, and I don't like the snowy foggy distance effect thing either. Didn't like it in Eviternity 1 either and thought it was the low point of the whole wad. Most of these levels feel indistingiushable, just the continually overly long and drawn out levels with too much to fight through. Seriously if I gave you a screenshot of any random room from these levels you'd probably not be able to tell which one it was. Breaking the mold is map 24, which while the longest of them all contains several excellent fights that would not be out of place in a truly designed-for-difficulty mapset and a novel ending challenge. Map 25 is a boss map which is pretty simple once you understand the Necromenace.
Episode 6 I like the overall look of but it's WAY TOO FUCKING DARK. I feel like these maps are designed to be played with a gamma level of like 1.3-1.4, not 1.0. Map 26 is an interesting "puzzle" map, but its doom-related puzzles rather than arbitrary stolen from outside sources puzzles like map 14. Individually they are interesting but collectively they take just too much time to get through. The final fight is set up to be an epic battle vs. a thousand enemies but the room is just too big, you can strafe around them too well, and the overpowered new enemies clear everything too quickly. It's more of just a bullet hell spectacle than a real challenge. Rest of the levels continue the formula of being a bit overly long and not challenging outside of some final battles.
Final boss is really cool, one of the few times I've thought that an FPS boss battle was actually well designed. Only downside is that unlike Eviternity 1 there's no awesome monster menagerie to fight along with it and watch the boss murder legions of trash.
Secret levels are a mixed bag, 1 per episode. 31 isn't that interesting except that its one of the few indoors maps that I think looks pretty good. 32 isn't hard but the final fight has a cool gimmick (you can choose when to electrify the ground and kill everything... which obviously makes it way too easy, I didn't even need to do it a second time). 33 is a speed running gimmick I couldn't finish. 34 has the one good use of veilimps in the wad with 2 archviles behind a horde of them and I was out of rocket ammo. Map 35 has a really, really cool gimmick wasted on a pathetically easy level. Map 36 is the epitome of a way too long level that with a bunch of fights that are way too easy once you have a basic understanding of how they work, though it gets props for a sort of inverse of the Sunlust map 29's archvile carosel which is a novel idea.