We flew Southwest Airlines down here to Las Vegas. It's not hard to see why they're doing well. They run the damn thing well, the planes are in good shape, and the crew clearly enjoys working for the company. Our steward was incredibly funny and everyone was nice. The prices were way less than anyone else too. I don't even mind the cattle boarding since we board early (see, Michael is good for something...)
Compare that to United, my normal carrier. You can almost smell death lingering on a United flight (watch for the vultures circling your plane.) What a difference.