I have read so many negative things about Spirit Airlines but they were almost $200 cheaper each way for my Spring Break trip to Myrtle Beach that I just had to try.
Advantage: they are the only non-stop from NYC. I heard the seats are small, but for 2 hours I can bear it.
Disadvantage: The nickel and diming: We are only checking 1 bag for the 2 of us, so $30 each way. $12 each to choose a seat, which we did - 2 aisle seats across from each other to compensate for the smaller seats.
No snacks or drinks, but we will buy something to drink at the airport.
We still ended up saving almost $200 each way, so I will see if we think "worth the savings" or "never again!!".