This is one of the items that is tested in your Windows 8 App when you use the WACK.

If you are in Southern California, please email these posts for more information on getting a token for your app by June 30, 2012!

 

Roaming application data lets users keep your application data in sync across multiple devices like their work PC and their slate at home. If a user installs the same app on two devices, Windows keeps the app data, like user preferences, in sync. This reduces the amount of setup work that users need to do for your app on their second devices.
To take advantage of this free, easy to code for, roaming functionality, check out the guidelines for roaming application data.
Become familiar with the APIs to check for quota for roaming settings. Though roaming is very easy to use, it is not designed to roam large data sets. Understand the implications and optimize your user experience accordingly.

Reference (HTML)

http://msdn.microsoft.com/en-us/library/windows/apps/hh465094

Reference (XAML)

http://msdn.microsoft.com/en-us/library/windows/apps/hh465094