A fan on 2ch has a list of expected differences between Final Fantasy XIII's demo and retail versions, cobbled together from statements made in Famitsu, Famitsu PS3 and Dengeki PlayStation. 1UP reports the list is everything that FFXIII director, Motomu Toriyama, claims will be changed. A bento sampler:
Battles will be harder in the retail version.
Players can issue orders to party members in the final build.
Most important: The Final Fantasy victory song will be present in the final game.
Check out the full list of alleged changes over at 1UP.