I've been looking forward to Dwimmermount for a long time now, and it's released! I wasn't actually part of the kickstarter (I almost never participate in those things), so haven't read the first draft, or been part of the drama, or any of that. All I care about is having another big dungeon out there, because I love big dungeons.
So - conclusion first - I really like Dwimmermount. It's really big, and it's full of pulp science-fantasy flavor. It is NOT gonzo science-fantasy - nothing like my own ASE that way. But you can see the shared roots, with floating space techno-gods, interstellar travel, metallized skeletons of unknown purpose, etc etc. So, James and I apparently read all the same books and watched the same cartoons.
What Dwimmermount is, is classic D&D. It uses tons of book monsters and book magic items. There's custom creations in there, but the majority of it is straight out of the rulebooks. It's also the product of play - my understanding is that James had a really brief set of notes and maps, and he made a lot of things up as he went along. This book is the actualization of that experience.
The side effect of this, is that this book is the realization of James' and his players' play styles. You can feel how his campaign worked and what his players were focused on as you read through it - it was an investigative, world-building campaign where the details emerged through play. That is a strength and a weakness here - to really get the most out of the dungeon, the players have to invest themselves in figuring out the details of the world. There are little margin notes that point out where history can be gleaned and sold off to sages - but it's a bit understated. I think the DM will need to create & use some NPC's to showcase this in the early levels to make sure the players understand that this is worthwhile - the text as written doesn't really cover that, presumably since James' campaign went that direction all on its own.
After the first couple of levels, the factions get all up in the players' face and the historical bits should fall into place much easier. This is very much a dungeon of factions rather than set-pieces and goofy traps - there's a lot of those, but the big deal here is interacting with the factions and playing them off each other. The factions and their motivations are very well covered.
Dungeon maps - very cool
Pulp background - very cool. It's got astral travelers founding subterranean cities, giant robot-gods, lakes of magic gasoline, really it seems yanked from a 50's "B" sci-fi movie
Wilderness maps & overview - a bit bland, but it's not really the focus of the book, so not much of a knock on it either
New monsters - a lot of these are copies of Labyrinth Lord AEC, presumably stuck in because of concerns about being "Labyrinth Lord" compatible w/o needing the AEC. Doesn't hurt anything, but could've been left out
New magic items - again, a lot of these are from AEC
I'm a terrible reviewer, others (Bryce Lynch, Gus L.) are much better at explaining why they like & dislike a product - but I've given it my best shot. Overall, I like Dwimmermount quite a bit.