Speaking to IGN Microsoft corporate vice president Marc Whitten said that the Day One update to the Xbox One console (the mandatory update you'll have to install before you can start using the shiny new next-generation console system) will take 15 - 20 minutes to download and install. The patch makes it so that the system can function both online and offline, but first you'll have to connect the system to a Microsoft server online so it can be patched.
"We are optimizing Xbox One so that the day one update is as fast as possible," Whitten said. "While we're still finalizing the details, we expect that the download will take between 15 and 20 minutes for most users."
Microsoft did not say how big the update is, but it will likely take up some extra space on that 500 GB Hard Drive...