I just used Airtran for BWI-Montego Bay last week. It is basically the same as flying USair in my opinion and a lot cheaper. I actually fly Airtran domestically about once every other month to visit my parents and never had serious issues with the airline. The Boeing 737 for the BWI-Montego flight is rather comfortable compared to their smaller jets they use for domestic flights. You may find leg room a little restricted if you are over 6ft tall like myself but this is normal for most US airlines. And unlike some US airlines, they at least give you pretzels or cookies on your flight. Plus, the Airtran flight got us to Montego Bay before 11am! More time to party!

A good resource I use when flying is www.seatguru.com It will show you which seats are the best on any flight.