It mostly works fine at around 6 feet for me, but I do feel like they expect me to go back further. In table tennis I'm right at the table and in most videos you see the paddle a bit further back. Maybe that can go away with tricking the calibration or whatnot. That's only for sports champions and games that make you do full body motions. Most of them can work as close as 3 or 4 feet sitting down like you would play the Wii. I'm sure Kinect will be similar and the 8-10 feet requirement is because it needs to get an image of your full body. At least with move, if you're too close for the sports champions games, the controller gets out of the camera's view if you extend your arm. That's more of a problem with how cameras work than the tech, though, you can argue that having a camera be so important to the tech is a bad idea to begin with.
And the camera resolution is VGA 60fps, 320x240 120fps. In good lighting conditions it is fine, but it has to calibrate to pick up the ball, which ends up making the imagine worse. IIRC Kinect's image camera is even worse with VGA at 30fps. It two more (?) sensors that make it better for games, but like the PS3 camera, the pictures it will take will probably be bad.