It's the only DDR that I've played for more than ten minutes, but:
- The songwheel is back
- Mission mode (now called Dance Master) is available from the start and is fairly involved. Secret missions, secret objectives.
- The corner buttons on pads can be turned off
- AA can only be accomplished with a full combo
- Rudimentary online play
I'm pretty much a DDR noob, so I don't know how helpful that is...