I've been Diamond for years. I fly every week and 95% of the time when I check in I am listed #1 for upgrade and if there is an empty seat in first, I get it every time. If I don't get an upgrade, I don't see it as someone with lower status got the upgrade due to a algorithm. I think there are lots of factors that Delta, or any other airline use to fill first/business class seats and it isn't just related to Medallion or freq flyer status.