I usually just lurk, but had to comment on this! I'm in Europe and this was released here last Thursday. Both my DH and I absolutely love it!
I've owned a Bodybugg for the last couple of years. I've been amazed by my readouts when I do DDR. After the initial beginning routines and trying to get the hang of it, I've been doing mostly Basic (opining to my DH that I'll never be coordinated enough to move beyond).
One am I did FIRM Body Sculpt (only cardio is tall box climb & leg press). My highest calorie burn was 4/min. In the pm I did DDR and my highest calorie burn was 10/min. Overall, I burned 3x as many calories doing 45 minutes of DDR than doing my exercise routine.
Obviously, if I were doing a Cathe step tape or a 45 min run, the difference wouldn't be as drastic. All in all, not too shabby for a video game, though!
The higher the BPM of the song and difficulty, the better the cardio benefit. If you have two left feet like my DH, it's much harder to work up a sweat.