When I was first silver in 2007 I had a very good upgrade % for ATL flights. I even scored upgrades ATL-LAX,SAN,PDX,SEA on weekends. After Delta acquired nwa life as a silver wasn't so great so I incorporated a couple of mileage runs to make gold every year.

I don't quite understand all of the hub to hub traffic. It just seems improbable that there could be that many passengers connecting to smaller cities only served by one hub. As an example I never missed an upgrade from MEM-ATL and vice versa on Delta before the merger with nwa. Now it is a shot in the dark on whether or not I'll get upgraded on that route. It just doesn't seem reasonable that there are that many people who need to make a double connection.