A couple of points here:
Space Mountain is my favorite attraction in Disneyland. This appears to be a substantial upgrade to Space Mountain, although it does lose points for being in a highly visible unthemed giant blue box. The ride itself is very hard to gauge, but I imagine that a significant chunk of the budget went to OLED (or equivalent) screens to keep things as dark and crisp as possible. I anticipate that the actual ride experience is more impressive / fun than any YouTube video could ever showcase.
The queue itself is sleek and befitting of what it's supposed to be, a Xandarian showcase. The humor seems to be on point and I'm curious if it's the same one liners on every ride. Did Drax make a "Ding Dang" comment around the Big Bang?
While Glenn Close's Nova Prime character isn't "evil" in the movie, she does give off some Tyra Banks / Chairman Clench / Alien Encounter vibes in her portion of the pre-show video. I'm not sure if that's by design or not, but it's interesting. Also, I love Terry Crews.
The queue area that has the news reporter interviewing the Guardians has a Q & A with Peter Quill talking about how he can't wait to go back to EPCOT and ride Horizons, see the Energy dinosaurs and sing Veggie Veggie Fruit Fruit. However, from a story standpoint, why would he be going to EPCOT? At this point in the attraction we are touring the Wonders of Xandar and our need for the Guardians is non-existent. What would bring Quill and the Guardians to EPCOT? Literally just a general visit? Does he want to check out the Germany booth at Food & Wine?
As for the "Does it fit in EPCOT?" question: I'm in the camp of "kind of". The lip service that Peter Quill visited EPCOT as a kid is pretty much just that. The experience could 100% happen without that narrative. We've come up with a means of traveling through time and space to go back to the Big Bang. Something that previous incarnations of the attraction in this space also did. Because this ruse is grounded in a Comic Book movie, it's going to rub people the wrong way. I'm not sure that disconnect is substantially different than Bill Nye, Ellen and Jeopardy bringing us back to the big bang. There's obviously nothing about energy as part of the attraction's narrative, nor are there dinosaurs. Something interesting though is that a power outage limits the Nova Corps' activity and moves the story forward, but it also could have been a window to allow for some discussion of energy sources. Somewhat interesting that they opted to not do that.
By all accounts, I'd say it's a better fit for EPCOT than the story treatment for The Seas with Nemo and Friends, Gran Fiesta Tour and Frozen Ever After. It's probably as thematically appropriate as Ratatouille in my mind.
The last point I want to raise is the cost. $450 million + is insane. Don't get me wrong, I can see where some money was spent, but that number just seems very high. I recognize that the omni-coaster is newish tech and perhaps a driver of this attraction. But I wonder if the story itself could have been told as a re-done Rock 'n' Roller Coaster.