Got to say, as an experimental platforming game mixed with music, it is pretty fun.
The tutorials get you up to speed pretty quickly. I was amazed at how well I managed the first symphony level they threw up. There does seem to be a little bit of intuition if you know the song the level is based on.
The song choices so far have been mostly classical music, though the last level before the first boss was a surprise: Madness' Our House. And that level was quite fun, I might add.
It's not going to appeal to everyone. Some might see it as a crappy platformer or a halfassed rhythm game, but for those who want both you can't find a better game on the DS.
Graphically, the game is pretty. The sprites are colorful and cheerful, the backgrounds are pretty well detailed. If there were a fault, it'd be that the top screen isn't really doing much during the actual gameplay. But with the level of attention this game requires, I can see why they'd want to avoid distractions.
I'd definitely rank this in my mind above Lego Rockband or Rhythm Heaven but right below Music Mon-Stars and Elite Beat Agents in terms of fun rhythm games.