Officially still a tech demo, this 3D Disk Scratching seems pretty well developed.
Nintendo was showing a demo of Activision's DJ Hero franchise for the 3DS. The demo featured a single song.
There were three types of beats: scratch, slides and taps. Scratches were shown as a series of arrows pointing up, for them you "scratched" the record on the bottom screen. For the tap notes you tapped the record and for the arrows you flicked the stylus to the left or right. It seems to work well, but I'm unclear how the note colors factored into the gameplay.
The 3D effect on the top screen showed the DJ seemingly leaping out of the screen, set against a 3D background.
The game seemed a pretty good, if simple adaption of the DJ Hero franchise to the 3DS. Hopefully we'll hear more about this game soon.