I think I'm going to be pretty meh when it comes to most CG/ML content coming into OFA unless I can figure out if, like iM@S2, 765 can also wear the outfits. Or if Kaede, but not holding breath.
What I personally wonder most is what the changes to the visual lesson were, since I couldn't tell too easily from the preview videos. Well, that and if the scoring system changed (which I hope it does, quite a few of the songs I'd have preferred using were "slow" ones) but I doubt we can figure out much about the latter until the game's actually released. I would also wonder about transfer of DLC, but, with the fact that songs which're standard for OFA were DLC in iM@S2, I doubt it. (It would defeat part of the point of DLC, at least from the make-as-much-money-as-possible frame of mind.)