Southwest Airlines has relatively cheap filghts out of Phoenix. Since they are based here, we get a good selection of places to go. I can usually book flights easily and there always seems to be availability to the places I go. The problem is the cattle service that you get. It really irks me not to have an assigned seat. I hate fighting to get in the lines, and the mad rush to the seats. It always gives me anxiety! There are always people trying to cram all of their luggage into every nook and cranny, and never a place for my one little bag, except under the seat in front of me. This is a pain, as my legs are long, and I like the little space you can gain from that area.
So, if you don't mind the hassles, you can get their fairly on time, and cheaply, but that is about it.