For those who have played the first KH final mix, you would know all the bonuses that it came with. I'm here to say that the KHII FM has crap than your ass can handle
Extended Worlds
New Spells
Bonus Cutscenes
New Weapons, including Vexen's shield for Goofy, Lexeaus's tomahawk for Donald, and a new Nobody Keyblade for Sora
All Organization XIII boss fights, including the elusive Zexion and the hidden Roxas fight
New enemies
Extended story for Roxas
The unknown fight(supposed shadowed character from the Sunset Horizon scene)
Harder 'Serious Mode' difficulty
Harder Sephiroth Battle
Tweakage on all the other modes
New Drive: Limit Form, where you dawn KH1 Clothes and regain all your abilites
and of Course a KH3/KH whatever Nomura plans on calling the last game Preview video
New PS2 version of Chain of Memories w/ trigger commands for enemies
plus much much more we have yet to see possibly… :\