It is a fantastic game in general, with a brilliant combat system which is a direct evolution of the KH2 one with a bit taken from dream drop distance (the fluimotion is still present, but less powerful than the DDD one).
Now the negative part: the story is really complicated, if you didn't play every single one previews game of the saga (including Union X), or if you didn't at least looked for a summary of all the story, you could find hard to understand a lot of details inside the game.
Next, the difficulty: now with the last update tath introduce the critical mode, the game offer difficulty level for everyone, from easy (very very easy) to critical (you will die probably 10/15 times for each world). Just be sure to make the right choice before to start, because if you change your ming, you have to start again from the begins to change the difficulty level.
Last, the characters: the growing of Sora is good, nothing to say about that, but I suggest to change the donald behaviour, make sure inside the settings that donald will heal (just you and himself) every time he can, or you will hate him after 2 hours. Don't forget to visit the little chef sometimes, to get some boost before the bosses (especially if you are using the critical mode)
But remember: this is NOT the last Kingdom hearts, it is the end of the Xehanort saga, and after that, you should wait for a far new chapter that will start the master of masters saga.
In conclusion: this is a great game, but if you didn't play all the saga, I suggest you to buy before the collection Kingdom hearts the story so far.
If my review was helpful, let me know with the buttons below