I had my thoughts written up patch day, but life intervened and kept me off the forums for a bit. (Also Tears of the Kingdom and an inexplicable urge to play FFVI PR.) Has it really been two weeks already? I can drop the play-by-play and limit myself to things I haven't seen pointed out yet.
MSQ
Zero - Zeromus link confirmed! Just, not something anyone had any reason to expect. There's an ancient hero of the Thirteenth named Zeromus, and Golbez just gave the name to his new toy to be ironic. Said hero is also the source of our Zero's name, and she's not thrilled about it.
Zero's 6.5 arc is looking to be a "real heroes don't exist" stock shonen manga crisis. A bit cheesy but, I mean, have you played Final Fantasy IV?
Pandaemonium
I spent most of the cutscenes hissing at Athena and don't really have much to add on the subject.
The incantation Athena uses for Ultima after the add phase is word-for-word the same one Lahabrea uses in the Praetorium Porta Decumana phase transition (in JP, anyway), which always stuck out at me because the EN script is trying really hard to pretend it's not a Slayers-style spell incantation for some reason, and just Lahabrea boasting like a maniac. Anyway, the callback was nice, even though it's (another) one of those points where the localization sabotages its own continuity.