The Xbox One's Kinect impressed us greatly over the hour or so we spent in front of it. Compared to the old Kinect it's like night and day.
The new Kinect understands your voice commands better, of course, but it also recognizes users as they step into its frame. Signing in and having the console display your items, pins and preferences is as easy as saying "Xbox, show my stuff," and it recognizes each user's voice as well.
One of the most subtle and impressive features of the Xbox One's Kinect occurs during Skype calls. When one person is in the frame it automatically zooms in on that person's face. When another person enters, it zooms out to encompass both users. It can also pan and tilt, and it's all done digitally; the sensor itself never moves.