By saying "Xbox on" you can turn on the Xbox One, log in using the new Kinect's facial recognition, and hit the system's dashboard, all within 13 seconds. At least, that's going by a video (see below the break) posted by Xbox spokesoldier Larry 'Major Nelson' Hyrb - and yes, we timed it.
In this case, the console's being turned on from standby mode, rather than a cold boot; as Xbox Director of Product Planning Albert Penello explained on Reddit, the 'Xbox On' command works when the system's in standby. Also, it appears the Major's signed into Xbox Live (as well as the console itself) by the video's end.
We'll all be able to test this out for ourselves in just over a week's time, when Microsoft's next-gen console launches on November 22, with a price tag of $500.