Well at first look at the game it looks like a great game. But when it gets down to it the deeper parts it falls short of being called great.
Nothing to complain about the story. The game spans out to 3 separate parts for 3 different characters. Then it joins together into 1 story at the end of the game. The problem is while it fills in the plot holes the previous games made. It creates twice as many new ones. Its not that deep of a storyline if you look at it without the other Kingdom Hearts Games.
What looks like a very good system of play. The battle system mainly focuses on your command deck to control your character. You can use whatever you like to play the game. Towards the end of the game the battle system quickly falls short. As a lot of your favorite commands become rather useless and pratically forces you to play a certain way to beat the game. Hit detection at many times is rather wonky as some attacks will target some random enemy or go into a completely different direction making you wonder what happened.
What's worse is post game or side quest content tends to be rather glitchy when it comes to your abilities. To be more specific when it comes to reading your abilities such as Leaf Bracer, Second Chance, and Once More. (More about that in my later videos of this game or on request.)
The music is great in certain areas. Others tend to be annoying despite it being fitting towards the current world you're exploring. The voice overs are nothing to truly complain about. Although at times Terra sounds like he was voiced by 2 different people. I do wish there was an option to use what music you wanted in the Mirage Arena. Other than that nothing really significant makes music horrible.
Game Length & Replay Value
The length of the main game won't last you long. Even though the game wants you to play it for 80+ hours for a pointless trophy. You'll be spending more time grinding and doing optional stuff than with the actual story. You can probably finish the game in less than 15 hours.
As for replay value I only had a few areas I would replay the game for. The post game stuff however is rather boring and frustrating to deal with. If you're really looking for a longer Kingdom Hearts Game play KH2 or KH1.
Overall this game isn't as great as everyone says it is. Its better than most of the Kingdom Hearts Games but that's not saying much. Its not horrible but its far from being a great game. Wait for this one to go on the greatest hits or find it for cheap. This is one of those titles I wouldn't pay full price for.