Kingdom Hearts fans need this!
The game itself is basically the same, but the animation seems much smoother and even more lifelike than the previous installment. Unfortunately, all of the text is in Japanese so you will need some sort of translation. All of the cutscenes have English voice-overs and Japanese subtitles. The new cutscenes added for this version of the game have no voice-acting whatsoever, but the subtitles are present.
There is also an unbelievable amount of new content for the game. A new mode is available from the opening menu called Theatre Mode where all the cutscenes are available to be watched over again. There are several new weapons for Sora, Donald and Goofy. New synthesis items and accessories are available too. A new form is available where Sora uses old abilities that did not make it from the first game, such as Ars Arcanum.
The best new thing about Final Mix is the new boss battles. There is a new feature called the Absent Silhouettes, which are battles between the dead Organization members from Chain of Memories without the card combat. Plus the cutscene where Sora and Roxas fight outside Castle Oblivion is now an actual battle. A new area is also available inside Hollow Bastion where all thirteen of the Organization members are able to be fought again. But these battles are much harder version of their original selves. The greatest part is Terra from the teaser trailer is available to fight over and over again. He is a very difficult foe to defeat.
Bottom line: Final Mix is definitely worthy of being picked up for any fan of the series. There is plenty of new content for people who already played the game.