Okay, I beat it about a week ago, now to wait for it to come out in English so I can really enjoy it.
[spoiler=New Plot Elements]Remember that "missing 75% of the story?" It must be hiding really good if it's here, there's all of one new thing added:
You get to play as Golbez in a flashback to when he was a little kid and Cecil had yet to be born. KluYa dies for some reason (Being able to read the text would really help) and their mother dies a few minutes later after giving birth to Cecil. This is apparently where Golbez's hatred towards Cecil came from...hooray clichés.
I really hope there's more than that and I missed it because of the language barrier...[/spoiler]
[spoiler=New Gameplay Elements]I didn't use the new command system at all other than reordering the defaults to my liking. You get more than just playable character commands though, you get abilities from the four emperors and a few other people.
There's a new game+ type thing after beating it, you keep all your commands but everything else is back to default. As I didn't have any commands equipped I don't know if the characters you give them to retain them or not.[/spoiler]
[spoiler=Other]Namingway gave me the music player but it never showed up in the fat chocobo's menu, I don't know if it's a bug or there's something else you have to do to get it permanently. I should check my new game + file to see if it's there.[/spoiler]
And there have been a ton of changes made to the enemies and bosses, most have been beefed up but a few have been nerfed (Blue Dragon is the most obvious one, it lost all its elemental resistances and absorption).