A good part of the puzzle in the world of Kingdom Hearts.
It is repetitive.
GOD it is repetitive.
You have 7 kinds of different missions: Tutorial, Hearts-collecting, Researching, Badge-collecting, Boss-battles and Bigger boss-battles and few in another category (which is 3 missions or so).
They are in 8 worlds, and even though that might sound like much (like a Mario-game), there are 93 missions (source: kingdomhearts.wikia.com).
That means you do those missions in 8 worlds with roughly 10 rooms you will see countless times again and again and again and again.
Do I overreact? No. Why? Because most of the worlds are completely copy-pasted from KH 1 and 2.
Now, I'm not going to review the multi-player part of the game (mainly because I've never tried it), but I have a hard time figuring out why that should be fun. the repetitive missions with 3 friends can be fun, admittedly, like a Tekken-game can be if you fight against friends.
You know what, scratch this part. I should probably go out and get me some friends (or a heart to begin with, hurhur, etc.).
Speaking of hearts (or lack thereof), the story of the game is as any Square Enix game you would expect to be. You get to know and love the characters, you get to cry in the ending (WHY XION?
WHY!). I must admit, however, I do miss a final boss like KH2, which was a strong person instead of a huge monster (and no, the last enemy ISN'T the last boss, but for story reasons, you'll get the idea). As said about, a good piece in the puzzle of the KH-universe.
Gameplay has almost no change except for the little panel system, which makes you customize your character's strengths (magic, melee, etc.) much better than in KH 1 and 2. A nice touch, which is something I actually hope the will try to keep, since it reminded me a bit of Final Fantasy 7 and 8 for some reason.
Last words: Even though it is repetitive and to some times boring and annoying, the story is just as great as Final Fantasy (in some cases, even greater). I usually say "If you want a story, go read a book or watch a movie", but with the Square Enix, I beg to differ. Seriously, if you want a part of a good story, go buy this game.