On iOS4, you need to trigger 3D acceleration to get acceptable redraw performance. You do this by using a 3D CSS transformation to move the object the user is d

On iOS4, you need to trigger 3D acceleration to get acceptable redraw performance. You do this by using a 3D CSS transformation to move the object the user is dragging (translate3d with a z value of 0). The upcoming iOS5 is much better in this regard, and makes just setting .left and .top acceptable, so you could also just wait it out.