#1. While it may have been true that prior to the day of the flight you were number 1 on the waitlist, it changes the day of departure to the DM list and not the waitlist that you were on. That is no one's fault; it is the way the system works. With good reason.

#2. The CS agent you spoke with made a commitment that she/he was in no way authorized to make. That's the agents fault not your's.

#3. You are not out anything other than a missed opportunity, there will be many more along the road of life, therefore the offer of an upgrade must be viewed as a bonus opportunity. UA is trying to make amends. Not all amends are fully restorative as this is sometimes impossible. And no, I don't think a guarantee to upgrade your next HKG-SFO flight to First is a reasonable expectation either.

#4. Based on your description of the events, the gate agent handled it appropriately and politely. It appears that the inflight crew set an expectation that wasn't met.

#5. And finally. It really is all about expectations. Your own were not met. That is dissapointing and frustrating. Sometimes I find myself angry as well but I get over it.