The thing that has been worrying me ever since Natal saw actual specs released was simply this: floorspace.
Natal (sorry, the new name doesn't really Kinect with me) requires a ton of floorspace - and I simply don't have that much to spare.
However, I am looking forward to the new Xbox 360. It seems to actually be very well ventilated, which is something I've been waiting for ever since the 360's "Problems" became apparent. It still has the disc-scratching problem though - which is kinda a bad move to not fix it, considering their new motion tech is going to require a lot of movement. One wrong movement (or maybe even a right one) and that's $60 down the drain.