OK – I’m back in the office now and can see that a really fast drag will cause the mouse to lose contact with the widgets, but a moderate-to-fast drag seems fine. I think its a reasonable expectation for users to move the widgets in a ‘purposeful’ way if they want to actual place them elsewhere, otherwise just close them altogether. Just my thoughts though.
Anyway, I added the z-index change to lift dragged widgets to the foreground, and then return them to ‘auto’ z-index when dropped. This is done with the addition and removal of a ‘.move’ class so that other CSS decorations can be applied during the drag action (such as a box-shadow).