Every airline has negative reviews. I've flown Frontier probably 25 times in the past 6-7 years, and for the most part, their service has been fine. The savings are incredible, but you really do need to be flexible or have a back-up plan in case of any flight delays or cancellations. My trips are usually for no more than 5 days so I do the backpack thing every time--it's a good size backpack that fits 2 laptops, 5 days worth of clothes, plus some other stuff. It will fit under the seat, but like the other commenter said, its not a problem to place in the overhead bin once on board.