honorbuddy: What's different in the game?
frostcircus: Unneccessary two-player mode, unneccessary English subtitles. You're not missing out on anything important (aside from non-horrific box art).
Not exactly correct. Several puzzles were made harder, an extra hidden weapon was added, subtitles clarifying the plot of the game were added for the second play through (which is also absent in the US version), and a second ending was added. So yes, if you care about the story of the game, you're missing a fair bit.
Whats wrong with ICOs? Sure it's not very good and looks bad in comparison to the non US versions but hey, Mega Man 1 and 2 beat it by a mile :P It damaged sales.