I haven't read all the posts, but let me just say one thing: I will NOT be flying Spirit Airlines anymore. Being in South Jersey, they were convenient and a decent airline, I thought. When they instituted checked baggage fees, I didn't mind much because other airlines had them. Now, this?!? No, thank you. They can kiss my business good-bye!
On a side note: when they instituted the checked bag fees, I had already made ressies. Wouldn't you know, when I got to the airport, the clerk tried to charge me? I had all my print-outs and confirmations, showing their policy, the "grandfather" dates as well as my original emailed confirmations. He was ticked-off because they didn't get any extra $$ from me! Ha!