Richard -- As a "lowly" Silver Elite, my upgrade rate is around 70% when I travel without my family -- and I'm starting at EWR. But, I can tell you that probably half the times I didn't get an upgrade, there were seats available (either for revenue or reward) shortly before they opened up for Silvers to upgrade, so I was probably beaten out by other Silvers. You will have a hard time getting F if you book same-day, because of the liberal upgrade rules for Silvers; if you know about a trip even the day before you travel (so you beat the midnight deadline), you should be OK.