If your Xbox One is set to “Instant On,” the next time you boot your console you will receive the first update in the console’s young life. Changes include the addition of a battery icon when you back out to the home dash, the ability to see HDD space, USB keyboard support, and unspecified improvements to the Blu-ray app (amongst others).
Also included was the quiet deletion of an ugly sharpening filter applied to 720p games. This was notable in Dead Rising 3 and Killer Instinct specifically. Those sensitive to the artificial visual touch up will note the more natural image quality when booting up those games.
The rollout is happening all weekend long so if it does not happen the next time you boot the Xbox One, be patient. It will come through soon. There is no option to manually check for updated firmware. This is an entirely automated process now.