Great concept, great workout - your body is the controller but I question just how practical the games can be. Yes we would all like to play Street Fighter for real and experience the excitement of doing a roundhouse kick full on somebody's face, but just how may rounds can you go without tiring yourself out.
And then Sony made the point themselves with FPS games which is one of the most popular formats on the consoles (COD, MOH, Killzone, GOW) what are you going to do, point your finger at the screen and go pow pow, duck behind the sofa for cover, run around your living room like a headless chicken?
I kind of suspect the games might be limited to synch games with limited appeal. I could be wrong.