The DragAndDrop behavior is having some trouble on touch machines with Windows 8 Release Preview. Some observations below:
I have a simple repro in this project http://sdrv.ms/N6gsoy
1. I have a ball sprite with DragDrop behavior set.
2. With Mouse it works as expected - I am able to drag and move it.
3. Touch with Chrome in Win8RP: I need to double tap the ball before "On DragDrop drag start" event fires.
4. Touch with IE in Win8RP: I cannot drag the object at all.
I am sorry I don't have access to any other operating system with touch screen. Please let me know if you need more info.