I fly spirit and have nothing but good things to say about it. I flew my family to Aruba for $150.00 round trip.
My brother flew it from Florida to Michigan and had nothing but problems. Stole his camera, seat did not recline, no t.v. , charged $50.00 for 3 lbs. over weight, if you want a drink or snack you have to pay by credit card and had no heat in the Spirit terminal when temperture was 20 below 0 outside. He had really bad luck.
So I guess you can say it is a chance to take.
Last July I went down on them as my airline was sold out. Service was minimal but professional and low-key. They do charge for food, drinks and bags but the rates can be absurdly low. Make sure you understand their rules and you should be fine. If you sign up for their $9 fare club, and have flexible travel dates, you can make out like a bandit.
Spirit Air flies to Aruba from FLL on Saturdays ONLY. If there is a problem with weather or anything else you are stuck! That is the reason we fly AA out of Miami. Obviously, Spirit would be more convenient but...... I don't want to have to lose a week of vacation.