Played a few songs with what little time I had last night after DL finished. Game is fun, UI is nice. Progression/level system seems interesting, haven't unlocked step play yet. Game throws a lot of explanatory text at you for each mode that I am too lazy to translate yet.
Songs I have played so far seem like full versions, pretty long.
I'm coming to this knowing little about Ia's songs in general, I only know a few (and those like 六兆年と一夜物語 isn't in the game, yet?).
Not sure what the clear criteria is yet, only played on Normal, which is pretty easy. Not sure what getting the Color notes does for me but change the UI a bit. I actually need to go back and look at some of the older preview videos, because the note system seems different. For example, haven't seen anything like this yet (where the notes are on their own 3d plane):
Perhaps with the long delays they went back to the drawing board a bit. But again, I'm only a few songs in.