The largest-ever update to arrive on the Xbox One is now rolling out to the public, delivering many promised features to complement Windows 10, and optimize the operating system as a whole. The update is seeing a staggered release, with different regions expected to receive the update during the day. The distribution process began at 12:01am PT worldwide, however we have yet to see users getting access to this release. The availability is dependent on locale, time zones and Xbox One settings, so it is hard to predict when specific consoles will receive an update.
If your console uses the instant-on power mode, the update will download automatically once it pushes to your console. The update will be downloaded while the console is in standby, before a final install takes place once powered on.
For those who do not use the feature, the update can be manually triggered via the Xbox One settings application. To start the update, navigate to Settings > System, where the console will check for updates, and prompt to download the latest build.
The New Xbox One Experience update will introduce many new features to the public, while massively improving both speed and stability. The user interface has been greatly refined, now streamlined to reduce time spent on simple tasks. Aside from the new look, the console will also offer "backwards compatibility", allowing select Xbox 360 games to be emulated on Xbox One hardware. Looking into the future, the update sets the foundation for upcoming implementations of other Windows 10 features, such as personal assistant ‘Cortana’, and universal application support.
The most recent Xbox One operating system build is "OS version 10.0.10586.1006 (th2_xbox_rel_1510.151107-2322) fre"
Source: Major Nelson