I looked at Spirit a few times. Of you travel with only one under-seat bag, it often is cheaper. If you travel with any more, they will nickel and fine you to death, and you'll often pay more than one of the majors.

So I never used Spirit, and never would have.

I flew Spirit from time to time. Not because of price, but because it was sometimes the best choice for scheduling. With kids in school and other commitments, for us the prime criterion for picking a flight was often the time of departure - late enough that the kids could have at least a partial day at school, but not not landing late at night.

The travel experience was....fine. Spirit's MO was not necessarily that they were offering a terrible airline, but that they were offering an a la carte airline instead of pre fixe airline. If you topped off to get the stuff that was included in a 'normal' airline ticket, it wouldn't be any cheaper - but it wouldn't necessarily be all that much worse than being in the bowels of basic economy on another carrier. If that's what we had to do to get that 3:45 departure time on a Friday, we were all for it.