I've tried it three or four times and it has never once worked for me. Apparently I'm a slow learner.
I've used it on two occasions before, and it seemed to work well enough? A tire plugging kit along with an outlet-powered air pump might be a better precaution than the fix-a-flat, then.
In spite of the incredible paranoia about "bad people" in the middle of nowhere in the desert - I have yet to meet even one. And that's after 30+ years of desert travel. There are some slightly weird and half-baked "desert rats" out there. They tend to be isolationists. But they're not serial killers. They just have a hermit kind of mentality, that's all. It would probably be socially unacceptable if you just went around shooting them :-)
I don't think anyone was advocating shooting hermits. I just believe that when you're in the middle of nowere with a significant wait for help, it is better to be prepared for the situations you can prepare for. One is far more likely to need a fire extinguisher than a sidearm, in most places, but having the capability of self-defense is never a bad thing.