I fly them at least 6 times a year these days and my boyfriend flies them to visit me as well. Mostly using Orlando, Myrtle Beach, Trenton and Philly airports. While I have read a lot of complaints about cancellations and delays I've only experienced one major delay so far myself. That was for a mechanical issue and lead to a 6 hour delay. But it was handled well IMO and we received a voucher for a future free flight. My impression with cancellations is that it's more out of areas that are less popular destinations, but cancellations can happen with any airline of course. The thing to realize is that if it does happen with a smaller airline like Frontier there are less flight options to get you home. Myself I'm okay with that because I'm usually flexible with our trip dates.
The airline works as any typical discount airline with a la carte pricing. But it's all on their website so nothing should be a surprise. We rarely ever check bags and if we do we go with one large bag for all of us rather than one per person which cuts down on the cost significantly. We also don't usually pay for seats and so far so good with being seated together. They do allow for one free personal item that has to fit below the seat so we maximize this and use a bag like a Vera Bradley Weekender or a good size backpack. Carry On luggage is more expensive than checked usually. Snacks are also extra but we usually always grab something at the airport anyhow.
