I had a good experience flying Frontier. I bought a last minute, one-way Frontier ticket because of the decent fare. After buying it, I read the many negative online reviews, so decided to build in extra time at Sky Harbor before my flight and lowered my expectations (and paid close attention to the number and size of my carry-on and personal bags- made sure I had room to fit my purse inside my suitcase so I could stowe my carry-on with books and computer at my feet.)  I ended up having 2 great, on-time flights, an easy connection, comfortable seats and an all-round satisfactory experience.  I fly often and like it when expectations and the experience are in sync.