I agree the worst aspect of Frontier is their constant route changes. I flew them a lot from ATL to MSY. The flights always seemed full, and their in flight product was good. Then after less than a year they abruptly discontinued the flights. I still fly them when I can but that is not frequently because they don't currently fly where I need to go.

They recently upgraded their frequent flyer program presumably in an effort to build loyalty, but it's hard for me to see how that can happen with a constantly shifting route map. True frequent fliers would be reluctant to switch. Of course they may be making enough selling points to the bank to make it profitable.