title: Flex 3 Tree drag-and-drop is slow
body: <p>I have another drag-and-drop question. I'm using DnD on a Tree component and it works fine, when I have up to 50-80 items in the tree. However, when I have 100-300 items, the simple drag-and-drop operation suddenly eats all my CPU capacity and the application freezes for up to 1 minute. </p>
  
  <p>I suppose that happens because Flex is trying to redraw the proxy dragImage and, thus, needs to redraw all the 300 nodes. Is there a way to turn off the dragImage? A simple cursor arrow with a small rectangle will be enough for my purposes.</p>
  
  <p>Has anybody else encountered this performance issue with Flex Tree component?</p>
  
  <p>Thanks.</p>