Note that UA did not deliver the passengers to their destination (GUM), but instead returned them to HNL. I'm sure that was easier for UA, but just one more (very significant) inconvenience for the passengers.
My wife, daughter, and I were on that flight. Don't know if anyone will see this so long after the event, but I can clear up some issues. United severely downplayed what was going on with the plane in their statement to the media. They said it was merely a cooling fan issue. But when I woke up, it wasn't just an odor, there was a smoky haze in the plane. At that point, it had not been announced that we had already turned around and were headed back to Honolulu. But ten minutes later, the captain announced that we needed to land on Midway, which would take 40 minutes from that point. It was obvious the situation was serious if he was willing to land on a runway not set up for big jets. He dumped the fuel prior to landing as well, to lighten the load so we could stop quick enough. But after landing, the pilot told us that during the flight, the electrical systems began to fail. He said the radar and the radio systems both went out. Something was burning in the electrical systems and knocking them out one by one. By God's grace, we made it to Midway before full failure. I was preparing my heart to meet the Lord. As for touring Midway, we could not have seen anything since it was in the middle of the night. And when the replacement plane came, we had to hurry and get seated to be able to take off before dawn because the albatrosses of Midway get active at dawn and daytime takeoffs and landings are impossible. It was quite an experience that I won't soon forget. If you look up any of the photos of us waiting in the gym, I am the guy standing with a red shirt, gray hair, and a camera bag on my shoulder with my back to the camera.