Well, just finished up the Mona domain, got the final Conch and all chests across all domains.
Mona's puzzles were like 10x harder than the rest. Most of the time it was figuring out which orientation the room was in compared to the pattern you were supposed to make. Anyways, that was a legitimate challenge for once, which means we're gonna see a lot of complaints on the survey I think.
Anyways, at this point, I finished everybody's themed domains with all chests, got all conches, and cleared all but Fischl and Mona's islands. I have a few side quests (that I know of) to finish. Otherwise, I can say that this was a very high quality event by MHY's standards. Lots of content, not a ton of repeating stuff regarding puzzles and chest stuff, which keeps you thinking on your feet. Also there have been a surprising number of secrets and stuff added that they didn't have to add, which I appreciate. The main story/Fatui subplot was boring, but the character moments are nice. Also, nice preview of a future character.
Also, it took me until the end of his quest to realize it, but Miitoboru is basically a play on Japanese/english word 'meatball'.