I have tried to use the drag and drop interface in WP admin for things like widgets while using a touchscreen and it never ends well.
Sometimes the widgets will fly down the screen way too fast, or accidentally get dragged into the inactive widgets, or another widget area altogether.
This has been a pet peeve of mine for a while now.
More and more people are updating their sites from smartphones and tablets, so there should be an easier way to update widgets and other similar drag and drop areas.
Perhaps a numbering system where you can edit the position within a widget area the widget should go (1 would be at the top, 2 would be second from the top, etc.). When saved, the widgets can be rearranged on the widget admin page.
For new widgets in the Available Widgets or Inactive Widgets areas, clicking on them could open a dialog box asking the admin which widget area to put the widget in, and in what numbered position.