We flew Frontier this year from STL to MBJ. wasn't bad. have had worse. getting flight info on their website was limited to the morning before for flight status as this was a charter flight. Flight home we sat in one of several rows that the seatback tv's were down. Kind of a bummer, but both flights down and back ran on
time.
I have flown Frontier on charter to MBJ out of STL. Flights exactly on-time or early, clean planes, friendly cabin crew. I have also flown them scheduled air from STL to DEN and had the same experience.