2. The question itself asks for comparison with airlines other than United. Again, the best place to post a General Travel Question with readership by non-United flyers would likely be here, IMHO.
Had UA put me on America's Worst last week, owing to problems not of UA's making, for a change (apparently the ATC in Chicago had a bad hair day). Two days ago, I was on PHX-DEN on a UA flight that was jammed with HP passengers who seemed quite happy to be on the flight. I'm guessing six of one, half a dozen of another, and UA's passengers are both more exacting in their wants and more tied to the mileage program (and half resentful of that fact) than a lot of other airlines', so UA gets the loudest complaints.