Story
While the setup is interesting, I was a bit disappointed it didn't go terribly far. Board Eden, fend off a Keyblade Knight (who is totally not Gaia), then fight Leviathan and Titan 2.0 to restore those elements to the Empty.
The first bit is usually the slowest, but... we'll get there, I guess.
Battles
The large number of ring-out mechanics got a bit frustrating, and I died. A lot. Still, the fights are interesting, and the bosses' relatively large HP pools right now helps you feel like you're learning as the fight goes on. Titan and his little car are particularly annoying, and make sure not to use your gap closer when Leviathan splits the stage!
Nomura's designs are also pretty cool...
Music
Nostalgic VIII music beside intense techno remixes of Titan and Leviathan's themes. Couldn't ask for better.
Future
Given there are six elements and we've already restored two, that leaves four battles unaccounted for. I wonder what they'll be...