spirit like air tran, nickel and dimes passengers with add on fees.
so make sure that you read the fine print.
Even with the add-on fees they are often cheaper than other airlines. My suggestion is to read up and know how they operate so you aren't surprised. I have flown them and the employees treated me well.
I fly Spirit Air from Boston to Myrtle Beach all of the time to visit family there. The Ft. Lauderdale flight has a layover in MB I'm pretty sure. The flight times are early, and yes they do charge you for carry on and checked bags, drinks, and snacks, but honestly if you can get one of their truly great deals it's a wash in the end. Plus you get to your destination that much earlier, sleep on the plane. My flights out of Boston have always been ontime, coming back they tend to be a little late leaving, but do a good job trying to make time up in the air.