Huge fan of Spirit here, but you get what you pay for. They are only worth it when you get a super cheap fare. Is service bare bones? Well, yes. But you will hardly get luxury service on any other carrier. My last trip with them was last month Fort Lauderdale-STI Some observations..
-Since the last time I traveled with them, they reconfigured the A319 to put one extra row of seats, making the seat pitch the tightest I have ever experienced on a US carrier. In order to fit all the seats, the economy seats NO LONGER RECLINE. I couldn't put my tray table all the way down. My belly got in the way. (That has never happened to me with any other airlines) They now have the maximum number of seats the FAA will allow on both types of aircraft (A319 and A321)
-Planes are new but FILTHY! They are no longer cleaned between flights. In fact in Tampa, as the arriving passengers were deplaning single file on one side of the jetway, the staff was already boarding the aircraft with departing passengers boarding single file on the other side of the jetway! (This is only possible for domestic segments)
-Flight attendants are really the luck of the draw with this airline, ranging from pleasant and friendly, to surly, to downright nasty. As the plane is boarding go down the aisle and takes anything out of the overhead bin that is smaller than a roller bag and tells its owner to put it under his/her seat. Even on Latin American flights, few flight attendants speak more than a token amount of Spanish. This becomes a major issue when explaining to some passenger that they have to pay for their water or juice and that the only take a credit card, or when the time comes to hand out immigration forms on flights to the US.
-During the holiday season, they will accept only ONE bag on flights to and from the DR (and some other destinations) and it cannot be overweight. Year round restrictions of one bag apply on all flights to and from Colombia, Peru and Haiti
All this aside, for round-trip flights under $200, it's totally worth it. (Assuming you aren't the type of person who has the compulsive need to take all your worldly possessions with you when you travel.) And they are profitable, so they must be doing something right.