I must've hit the jackpot with my agent tonight... have PS booked for a flight next month and called to apply a GUC. Agent knew exactly what to do, put me on hold for at most 3 minutes, came back and said the cert was applied and ticket reissued. Receipt shows OV for confirmed domestic F and intl D1 upgrade. Made sure to give her a 5 on the survey.

One interesting thing about this booking... the PS booking was a P fare, and I didn't see Z available when I called so was expecting to go on the waitlist. Surprise, agent said upgrade is available. So I wonder if there is some other hidden inventory bucket depending on fare?