It really is a great accomplishment.
However, when considering the following facts:
-Kinect is 150$, iPad is like... 400$ ?
-The Kinect Marketing push was much bigger and more expansive.
-The Ipad wasn't released during the holidays.
It makes senes that a device like the Kinect, that is very unique, will sell so much, in such a short time.
Bet with Dr.A.Peter.Nintendo that Super Mario Galaxy 2 won't sell 15 million copies up to six months after it's release, the winner will get Avatar control for a week and signature control for a month.