Microsoft's own video showing the Xbox One's dashboard and user interface was disappointing, because being so heavily staged, it didn't give us an idea of how it actually performed in the real world. This real video, on the other hand, is just perfect.
Shot in the middle of a round of Killer Instinct by Gameon Daily, it focuses mainly on how the system's menu and other apps can "snap" in on top of your gameplay, but also shows the user returning to the main menu as well.
Looks fast! And, when you simply must resort to GameFAQs, incredibly useful as well.