Currently on Windows Phone and Windows 8, you can download an app or a game for free as a trial, and if you like it you have the option to pay and simply unlock the entire app/game without having to re-download. The same did not apply on the Xbox One, where game demos and the full game were separate applications.
That changes as Microsoft has recently updated the Xbox One to allow for in-game upgrades. While the functionality was previously available on the Xbox 360 for Xbox Live Arcade titles, it was not available for the Xbox One at launch.
"When Xbox One launched you could do game demos and you could do games. But we didn't have the functionality that was on Xbox 360 - that 'trial' experience where you could download a demo and then convert it [to a full version]." Said Microsoft’s Chris Charla, head of the ID@Xbox program.
While there are no Xbox One titles currently available that make use of the functionality, future titles will be able to do so. This means that games will have to be downloaded in their entirety, even if they are limited in functionality as a trial. That may be something gamers will not appreciate if they have slower download speeds.
It seems that the functionality will be limited to indie (ID@Xbox) games only, with no mention of whether titles from big-name developers will also have the option to offer it.