Southwest is a major. Plain and simple. Sure, thy don't have the long haul international routes. But all of those little, short hops add up. They always turn a profit, and that says something in the airline industry.
If you live in Dallas, and travel on business (or even for pleasure) heavily to other cities in Texas, OK (Houston, San Antontio, El Paso, Lubbock, OK City, Tulsa, etc), Southwest should seriously be considered, especially if Love Field is more convenient than DFW.
I haven't flow Southwest it several years. Being Platinum on AA, it would be tough to go back to SWA. I can't stand the boarding process. Awful. I wanted assinged seats, and I don't like havign to get to the gate super early just to get a decent seat and space for my stuff.
But their award program is stone simple, just like everything else they do. No black outs, no capcity control. No endless array of awards. They just mail you flight coupons as you earn them.
The companion pass can be of great value, unless you travel alone all of the time. Think of how much value this has for small businesses. Think of the value it has if you like to travel around Texas for leisure (its a big state. Flying is frequently the way to go)