Now on to the details:
Overall, I can't help but feel like the episode was written with the instruction to "make it feel like the season finale and stick an open end to it". Not that that's a bad thing, quite the opposite actually.
Probably the main reason why it felt like this is the amount of loose ends it ties up: What happened to Naomi, Hachi and the original Nana, how the parasites live after the huge battle, how the remaining Nines cope with having outlived their purpose (the "and outer space doesn't sound too bad as a resting place" is probably one of my favorite one-liners from the entire show), what's the deal with Hiro's horns,...
As for Zero Two: Not exactly a new concept, but well enough executed to not be spotted immediately, and it resulted in some good-looking shots (also, I really like the look of bandage Zero Two). Also, the breakdown of Goro after Hiro announced that he will go save his waifu was probably one of my favorite ones in the series so far.
Now predictions for 23/24:
-Mitsuru and Kokoro are bound to regain their memories one way or another (I would love to see an "asymmetrical regain", things like one before the other, or them starting to remember different events initally)
-following that, they choose to ignore the "pregnant women can't pilot" thing, outcome unsure, either success and deus ex machina in space battle (which is the logical event, as Kokoro already piloted while being pregnant) or something goes horribly wrong one way or another, and they have to watch helplessly (I don't think it's exactly likely that they decide to pilot, but it could be nice to see if it was the case)
-The series can only really end in four ways, if you ask me:
1) Hiro stays in Strelitzia Apath with 02 while the others return to earth (probably without the Nines which sacrifice themselves)
2) Mitsuru and Kokoro being the only ones of Squad 13 remaining on Earth, while the others all stay in space, dead, alove or something in between
3) Mitsuru/Kokoro also going to space and staying there
4) everyone (except maybe the Nines) returning for WAFF-ish ending
...this was not nearly as structured as I hoped it would be