I think the demo was really enjoyable! I'm forced to use a new time method so I can play it as many times as I want to before the game reaches store shelves!
The controls are really good and the flowmotion is easy to use once you get the hang of it. I love how many commands there are for the flowmotion system alone! Makes you feel like a bad ass and it makes traveling around worlds easier and faster too! If you like Birth By Sleep, then you'll have no problem with the controls at all.
The combat is fast-paced and challenging. From what others say this game is the hardest Kingdom Hearts to date. I'm glad it is because 2 was way too easy. You have many choices on how to defeat your enemies. From regular combat, commands, dream eater link attacks, or flowmotion. Whichever makes suits you
Speaking of the world itself, the worlds feel much larger now than just a straight line towards the next area. Of course I'm talking about the full game not the demo. The demo will give you a good feel on how much larger each area will feel now thanks to the flowmotion system.
The graphics are really beautiful, one of the best looking 3DS games to date. It almost feels like your playing on a console, but your not! Also, the 3D is used really well and doesn't cut the framerate at all.
One problem I do have with the demo is that it makes you feel too powerful. In the demo you get many late game abiltities and commands so don't expect that when you first start the game. If you want a good look play the tutorial and run around Traverse Town because that's how you really start off. Also, why isn't Riku playable?!
That's pretty much it. The demo has me really excited for the final game. I wish the demo was more like the ones you get from E3, but it will do until then.