Among other things, several unlockable mini-games, videos and new weapons have been added to the collection. Also, the four characters introduced in Power Stone 2 are now playable in the first game. The collection also integrates the PSP's media functions by allowing you to pause the game, rotate the camera and take screenshots to capture your most glorious moments.
Capcom seems to be reconstructing both games as faithfully as possible - adding just a few new features to make the games more playable on the PSP, and enough new content to keep you unlocking things for a while. They certainly haven't subtracted anything, which should please fans of the series when it arrives in their hot little hands in October.