I woke up this morning to find that an entirely new user interface for my Xbox One downloaded and installed overnight. Still groggy from my Fallout 4 and Rise of the Tomb Raider marathon the night before, it took me a while to reorient myself to the new experience.
Aside from rearranging the look and feel of the Xbox One interface, Microsoft says the re-imagined Xbox One experience is faster and more social and now powered by Windows 10. An added bonus, all Xbox One owners can play select Xbox 360 games on Xbox One at no additional cost with Xbox One Backward Compatibility (provided you already own the games to begin with, ok). If you have auto updates enabled in your Xbox One, the update should already be installed or coming later today. It's magical. More information can be found here.
Source: Microsoft