Had the game for about a week now and it is awesome. I've been playing on and off and I've managed to get up to Hard Rock with the Elite Beat Divas and haven't been bothered to clock it on that difficulty, I may do that tomorrow.
Music makes me enjoy games, and guess what, this game is a music rhythm game! I was sad to have no ps2 or x360 to play guitar hero (the best game ever made), but EBA seems to do a good job of filling that spot.
I'm not sure how hard it's gonna get on this difficulty, but I've been hoping for lots of double tapping bits from one side to another (so you have to move real fast). I was also hoping for something like DragonForce for a final bonus song which woulda been fun but oh well.
The thing that annoys me in single player is the fact that getting notes correct hardly raises the bar and sometimes it can actually drop faster than what you're getting right, even if you're getting them all in a row.
Overall, awesome game, in my top 3 for DS atm. Agents are GO!