Rock Band Blitz should be 3D compatible.
Also We should be able to use our instruments if we choose to. For example If I want to use a guitar, holding down the corresponding color, plays the corresponding lane. Or for instance drums hitting the corresponding colored drum pad determines which lane you are playing in (Of course you would need at least one cymbal designated for the last lane)
I think it would feel more familiar and probably seem more fun if I could hold down the green fret and strum the notes of the drum, Switch to the red fret and be playing bass, yellow guitar, and so on.
And I think 3D on this game would really help bring you into the experience, and make it less iPhone game feeling.
I know not everyone has 3D setups but throwing on my 3D glasses and guitar would make this game a blast.