Its biggest problem is the gargantuan amount of space it requires to operate properly. I can't fathom anyone having that much availble space to hand, without moving around large quantities of furniture. Great for the 1st few days. But after that, i reckon you'll look at your Kinect, look at your sofa / coffee table, bed / walls etc and say nah, can't be bothered to move that to jump up and down like a buffoon.
I had one and a large playing space. Far larger than what is availble to most UK homes. During its calibration, it kept telling to go back, go back, i ended up saying the hell with this. Sold it after a couple of months.