In addition, the prevalence of discounted first class seats has increased. so now I can fly to the west coast on a confirmed A class ticket for only $50 more than the equivalent of the cheapest economy ticket plus the equivalent price of the 500-milers if I were to buy them. That's what I do, which means fewer last minute upgrades, I guess.

But I also agree that when I do use the 500 milers it is much more difficult to snag an upgrade than in the past.