All four legs of my trip were without incident even arriving ahead of schedule --- YAY!!
I've traveled Frontier before. The only reason I stopped is because my destinations connect through Denver with ridiculously long layovers. Nothing has changed from then to now, and I won't pay to sit and wait - hours! This flight was free through their Early Returns Program. They are clearly NOT the airline I remember.
Nothing is free! Everything will cost you! Oops, I take that back. A cup of water in-flight is free and also one item of carry-on to put under the seat in front of you. In case you're wondering, a purse is considered one item so use a backpack if you will have something else. Anything more and you will pay. Also the fees vary - checked bag vs. carry-on, and advance payment vs. flight time.
They charge for seats too if you're willing. I wasn't, and out of four legs got three aisle seats and one window (and yes, the plane was full.) There is very little leg room and don't count on reclining seats. My result was 50/50.
Please understand their check-in policy!! You can do so online and print your boarding pass but if you will check luggage your MUST do so BEFORE the cut off time - skycap or counter doesn't matter.
The flights are dirt cheap. They make money on baggage. Do the math before buying a ticket. The fees will add up. Quickly!