The other thing that got to me about that article is that with the very last technique--manipulating an electronic boarding pass to jump to the front of the line and get carry-on space--the author admits that this is at the expense of other passengers. As if they believe, or expect the reader to believe, that the rest of the techniques aren't designed to get things that otherwise would go to some other passenger.
If there was an unlimited, or even adequate-to-demand, number of upgrades, seats on a different flight, etc., none of these techniques would be needed. I would be more comfortable if it were presented as "some other passengers are using these techniques to improve their chances, you should know about them too" rather than "here are a dozen ways to get an advantage over the other passengers, but we're going to pretend that most of them are you vs. the airline, in a vacuum." Yes, it's worth knowing when to call the airline for rebooking rather than waiting in a long line, but don't pretend that this is just to save yourself time standing in line: it's to improve the odds that you rather than someone else will get that last seat on the flight to Pittsburgh. I think the only non-competitive thing in there was "don't check a bag, going carry-on only gives you more flexibility."