Southwest is the airline equivalent of Greyhound, with everyone getting on using grocery bags for suitcases.
I'll gladly pay a little more to get a reserved seat, and not have to listen to the lame company-assigned joke-of-the-day from the stewardi.
For flights under 2 hours, SW provides outstanding value. But if I'm going coast to coast, or longer, I'm gonna need a bit more luxury. I'll endure the flight to Vegas however, if only to save the money so I can give it to the casino when I land.