Bill,

There are a lot of similarities and differences both between SWA and Wal-Mart.

Similarities:

Low Price-typically, although not always
Friendly and prompt inflight service
Tremendous Market Power (not necessarily a good thing for some- and I'm no fan of Wal-Mart)

Differences:
SWA's decent pay for workers (best compensated flight crew for 737 A/C).
SWA wants to keep employees, not turn them over so they can avoid paying benefits.

Without naming the guilty legacy carrier- I've seen a Senior Flight attendant do a quick coffee service on a 1/3 full A/C and then sit across the aisle and open up a newspaper- she was done for the flight. Too bad if I wanted any more coffee, it was clear she didn't care. On another, different, carrier- I had a First Class upgrade (through luck, not Frequent Flyer miles) and was approached by the F/A once. I thought, "Wow, why would I want to fly this airline when this is what you get in First?"

Since frequent flyer miles can be difficult to redeem and you're only getting a soda and snack anyway, friendly employees are probably the major differentiating factor for a lot of people. The "cattle-call" line up bothers some, but other than that the seats are the same, if not better.

I'll finish with this- I don't think I've ever had to push any call button on SWA to ask for anything. The cabin crew are continually walking up and down the aisle making sure you have what you want. That's why I continue to shop there.