In promotional videos, Microsoft shows the Kinect's voice recognition working perfectly every time. When they want to mute it, they say, "Xbox, mute," and like magic the audio cuts out. In reality, it goes more like this: "Xbox, mute. Xbox. Xb--... Xbox, Mute. Xbox, mute. X. Box. Mute. Xbox, Mute. Xbox, mu--oh there it goes." When it works--hooked up to all of your entertainment devices--it's an amazing thing. When it doesn't, you spend more time telling your Xbox what you want it to do than it would take to just do it on the gamepad.
And even when it's working, there's the problem of remembering all of the commands. Though "Play Dead Rising 3" might make sense, you actually need to say "Xbox, go to Dead Rising 3." The system doesn't allow for much wiggle room, and if you don't know how to snap or unsnap something as soon as you want to you could end up spending a lot of time having one-sided conversations with a camera.