I've been upgraded 3 out of my last 4 legs - all but one was at the gate. I think it is more to do with the extra flights loaded up for summer schedules and the general slump in business travel this time of year.
After hitting only 2/48 F upgrades (and maybe 12-15/48 C+ upgrades) in the first 4.5 months of the year, this has been a nice treat.