It also includes all the cutscenes from the PlayStation version (which are also optionally integrated into gameplay). The best part of this is the built-in Sound Test feature. As you encounter monsters, learn techs, and get endings, they'll appear in the menus, with various informative details.
For better or for worse, the names of things remain more or less unchanged from the earlier US release. The translation has been slightly revised.Now, my memory of playing the original game is a little hazy by this point, but as far as I can tell, the changes are as follows: The DS version sure packs a lot of bonus material, none of which detracts from the game, but none of which is really, ultimately, necessary.
It was a special experience revisiting this game - one I've placed among my 2 all-time favorites (with only Super Metroid as company), but have not played in almost a decade. I've finally finished Chrono Trigger DS (including the bonus dungeons and the special ending, but not all of the original endings).