The company I work for in northeast Mississippi sends people all over the country regularly. We've used Memphis for years, but recently it's become a lot more difficult just to get where we need to go starting from Memphis, and the prices are steadily climbing to boot. In many cases it's now become barely possible to start from Memphis, fly to another hub and make a connecting flight to a smaller city in one day. One weather hiccup and your *** is an airport somewhere overnight.
GTR (Columbus) used to be a good option when Delta flew from there to both Atlanta and Dallas, but they dropped the Dallas flight years ago. If you're heading somewhere west of the Mississippi, adding two more hours of flying time to go to Atlanta then come back is a mental pain if nothing else. We've used Southwest some out of Birmingham, but what I've priced on Southwest out of Memphis has been no better than anything else so far, though admittedly these are all anecdotal examples.