I think I have been upgraded via ATL on two flights since making FO last November:
12-29-2011 - ATL-PBI (holiday travel, 757, K fare) - battlefield upgrade
9-4-2012 - HOU-ATL (Tuesday after Labor Day, CR-900, T fare) - window upgrade
It does happen, but probably not if you're flying to any sort of business destination.
Last edited by eturowski; Sep 13, 2012 at 3:22 pm