Is there any other "hard" boss besides the story lines?

Like Emerald and Ruby weapon in VII.

Penance + dark aeons (not all of em - mainly bahamut)

FFVIII's Omega weapon

Just in FF10

the US version you dont have the features of the dark Aeons or penance even break damage limit, thats all in the international version.

So, there's no optional bosses? Im pretty bummed now..

yea its a shame bro, when i moved to America from England for 3 years, i refused to play the US version, ever since i already beat the International one with all bonus features, just wasn't the same without them.

Wow, wasted a lot of hours getting everybody's sphere grid entirely covered....

Everybody is 9999/999

damn, must be a bummer mate, tho the story is still promising, but i see what you mean, the extra bosses and break damage and health limit gives it that extra kick to the game. im trying to find you a link, on google some where giving you the differences so you can see what differences there actually are. sorry to let you know.

http://www.gamefaqs.com/ps2/197344-final-fantasy-x/faqs/41079 scroll down a little and it tells you here mate.