It comes down to what you want do with your career. I couldn't imagine being 64 and being a captain on a 737 and flying four segments and ending up in ONT in a Holiday Inn with a 10 hour layover. For a lot of pilots, the stability of SWA is an attraction.
9/11 changed the equation for a lot of guys who now are around 40-45 years old today. A low hour CA at a regional went to FO. Regional FOs lost their job. Low hour FOs for majors had to scramble to find jobs. I went to a university that produces a lot of pilots, I only know one guy who kept with it after 9/11 and the layoffs. He was only promoted to AA FO from Eagle a few years ago. Another guy I know is now a partner in a venture capital firm after losing his UA 737 FO gig. He landed on his feet, certainly.
I've never run into an FA or pilot that has a bad thing to say about working for Southwest. My father, who works in sales, flies them exclusively for business.