I think the information on the app is significantly better nowadays. At one point right after the merger, they would post flight information that would be impossible to achieve - for example, having a departure time before the inbound plane's arrival, or only 15 minutes for the flight turn. Nowadays, with the gate agent writing out these lengthy novels describing the circumstance around the delay, there's more information on the app than before. The major discrepancies between flightaware and UA app come about when there's an aircraft swap, and Flightaware is usually right. I would then confirm the change with a UC agent (assuming I am waiting in one) to get the true story.

This is pre-iPhone and apps, but on a delay out of RNO to SFO, I remembered chatting with the FAs in the rear galley, and in comes a text from UA with a revised departure time in 20 minutes. After I showed the text to the FAs and telling them we are leaving, the captain announced on the intercom that we are going.

It's one of the few times I felt like an Oracle.