After months of teasing, beta testing and announcements, the Xbox One's big update for Windows 10, an all-new UI and backwards compatibility with some Xbox 360 games will arrive tomorrow. According to Major Nelson, the new software will start rolling out at 3AM ET, although we wouldn't advise waiting up for it for a couple of reasons. First, it's a staged rollout, so you may not get it right away. Second, the ability to play Xbox 360 games (here's the list) won't switch on until 3PM ET, so you've got some time to get ready. Finally, assuming your Xbox is setup for "Instant-on" it should automatically grab the update and install it without you needing to do anything at all. The new Xbox One dashboard has a completely refreshed layout, but there's a lot of info availableto help you get used to it.