All in all, not bad. While there's no telling how easy it will be to book upgrades with the Global Certificate, I will start to inquire when making other bookings, just out of curiosity.
Hopefully this may change, but reading the T&C, I see: "Airport standby is not available on Air France or KLM operated flights as well as Delta operated flights originating from AMS, BOM and CDG."
At least for me, those AMS/CDG DL flights would be where I'd love to use the upgrades I accrue.