I thought that I would update this with my recent experience, on our first segment there were no available F seats on the A319, however on our connection at IAH the ERJ-175 had 6 open seats with only 2 on the standby list. I had received an upgrade at the 96 hour window.The agent at the United Club was unable to help, she could only find upgrade options using miles or $. At the gate the agent was not able to process the upgrade, however she referred me to an agent at a nearby gate. He was able to add my wife to the list with a few keystrokes, returning to the gate the upgrade was cleared before boarding. The fact that I was on a reward ticket was never raised as an issue.