I've used Frontier and had no complaints. But then I'm all about cheap flights as I've been making 8-9 trips a year for the last few years. However I should state that the longest flight was just a little 4 hours and most of them only 2.5 hours. I would certainly be willing to pay more for comfort on a long flight like to Hawaii or Europe. Also we don't have long legs and are able to fit in the seats on all carriers. Staying at the timeshares with a washer and dryer we find that we are fine with sharing one checked bag and our personal item bags that fit under the seats in front of us. So we aren't paying for any of the extras other than one shared checked bag.
For our personal travel we haven't used any carriers other than Spirit, Frontier and Allegiant in probably the last 5-6 years. Of those three Allegiant is my last choice as they are small and don't have the extra planes and crews to bring in so their schedules can sometimes get significantly delayed when you have late afternoon and evening flights.
As other people have posted flying is not the luxurious experience it was 40 years ago. I simply want to get from point A to point B on a non stop flight if one is offered as cheaply as possible as long as the flight is no more than a little over 4 hours. I have so many other things that are actually fun that I would rather spend my money on. Paying top dollar for your flights is no guarantee you won't put up with crying, whining children, farting or otherwise smelly fellow passengers, obnoxious or drunk people, etc., as evidenced by the many stories people recounted here and the stories we read online.
IMO having to plan to be at the airport so early, the drive to the airport, checking your car at the off site parking and being transported to the airport, going through the lines checking bags, checking tickets and security, being packed on a metal tube with numerous other people hurling through the air at high speeds is never going to be the highlight of my vacation so why pay any more than absolutely necessary. I'm more than happy to bring my own little snack or sandwich, fill up my empty water bottle before I get on the plane, get myself settled with my neck pillow as I usually manage to sleep for part of the flight and my book to read for the rest of the flight. i get off the plane ready to enjoy my vacation. The flight is the means to get to this vacation not part of the vacation experience. I'm not Jennifer Aniston flying in the Emirates Airlines commercial and I don't need to be to have a wonderful time on my vacations.
Spirit Airlines $134.40 total for 2 people with one shared checked bag each way, round trip non stop flights from Cleveland, Ohio to Fort Lauderdale, Florida, and the return trip, February 13-March 8, 2017. There were quite a few other dates available at this price when I booked these flights a few days before Christmas but these were the dates I wanted.