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 this post for more information on getting a token for your app by June 30, 2012!
Metro, Metro Design, Windows 8, User Experience
To allow your users to switch across apps and feel like they never left your app, you must properly and efficiently handle the process life cycle management (PLM) events. At the highest level, you should:
Save transient state on suspend Handle the resuming event, update the view if the content has changed since it was last visible to the user Restore the transient state on launch event when the last known state was terminated
To learn more about PLM events, follow these guidelines for suspend and resume