I survived my first Frontier flight. I will never fly them again for cross country flight, but it would be fine for a flight two hours or less. It really is bare bones. The seats were like sitting on folding chairs.
They just started in Columbus recently and I flew them from LA back here, via Denver, this week. It was fine. I had an assigned seat, the plane was on time and comfortable, the ride smooth, the staff friendly enough (not Jet Blue friendly, but fine).
I’ll fly them again because they are SO cheap. Their $2 sodas and bag fees don’t bug me at all, I pack light and always have a water bottle and my own snacks. It is worth making sure that they are still cheaper after you add back the fees.
That said, I’d love to have Jet Blue here again. They came and left 
@OHMomof2 Yes, I brought snacks with me. The seats just were not that comfortable for a cross country flight. I also let me D1 have the window seat.
I flew Jetblue for the first time last summer, and I LOVED it!