I tend to forget to press the Back Button & just press the Windows Button, as coming from Android I'm used to the Back Button just backing up in an app then minimizing it and then having to use the Multi Tasking Button to close. So just tend to us the Back Button as a Back Button in apps & as the Multi Tasking Button, don't see the point of Closing 6tag to write an SMS then having to open 6tag agin when I can just press the Windows Button to get back to the Start Screen then open 6tag & then Multi task between the 2, GDR3 has done away with the need for the Back Button as you can just Close apps from the Multi task Window.
I'd put the Back Button in the App menus & make the current Back Button a Multi Tasking Button to bring up the open app list since GDR3 has introduced the Close Button on open app tiles to match IE tabs Window. I'd even take single press of Windows Button to go to Start Screen, keep long press as it is now, add double tap of Windows Button for task list & make the Search button a fixed bar at the top of the Start Screen with a press of the Search Icon to open a window that allows the selection of QR Code Reader, Local & Sound Search while pressing on the Search Bar brings up the keyboard and allows you to search directly instead of opening Bing to then Search.
Roland