We're going to have a few posts this week up on the Office Next blog that drill into the new app model from three perspectives: the end user; the developer; and the administrator. This first post that goes into the end user experience is now live: http://blogs.office.com/b/office-next/archive/2012/08/06/introducing-apps-for-the-new-office-and-sharepoint-and-the-office-store.aspx