I always fly Southwest....unless I physically cannot get to my destination by flying with them. A few times I have flown as close as possible and rented a car to get me the rest of the way.
I think their prices are low, I actually do not mind the boarding procedure because I normally fly alone, their frequent flyer mile program is awesome and I get many free flights a year, and if they take off on time, you always land early...if they leave a few minutes late, most of the time you still land on time.