I have flown with AA, Continental, Delta, and JetBlue. JetBlue is the best in terms of comfort, reliability, courteous service, and being customer friendly. All the airlines are similar in costs, and you have to research the best price each time you travel, but if the costs are comparable, JetBlue is the winner, hands down.
I like two, Continental and Jet Blue. The decision as to which to use depends upon price and flight times. The only drawback to Jet Blue now is that they will charge $20.00 to check a second bag while Continental does not do the same on international flights.