Terrible Mechanics that ruin an otherwise great game.
Firstly, as a kingdom hearts fan, I wish they would stop making these games handheld, as they are not games to play for 5-15 minuets, thanks to save points sometimes being some distance apart, and frequent, sometimes lengthy cinamatics. A game like this would be more comfortable played on the tv over in your hand.
Flow motion, this games biggest change to gameplay, can be a fun, if a bit overpowered addition to gameplay, that makes the normal kingdom hearts fighting nearly irrelevant. why bother with normal attacks and magic combos, when you can just run over to a wall and spam flomotion attacks until everyone's dead.
Thirdly, the game is set between two alternate worlds, one where you play as Sora, and the other as Riku. This would be a cool idea, were it not for the drop in/drop out mechanic, where after 20 minuets or so it forces you to play in the other character's world. This will happen regardless of your situation, whether you are fighting monsters, managing inventory, fighting a boss, etc.
Finally, as interesting as the story will be to kingdom hearts fans who have managed to follow along through the past six games, to anyone new to the Kingdom Hearts series, it may come off as a convoluted mess.
Despite these complaints however, this is in no way a completely terrible game. The art style is unique and strange, the combat is fast-pased and enjoyable, and the voice acting is superb, and this is easily the best looking handheld game I've seen so far.