I know that this has been debated here on DD Forum for a while, so I recently made a couple of phone calls to Spirit, and spoke to a couple different representatives, and here are the actual details:
Sign up for the Spirit Mastercard, and receive 15,000 miles. You can get bonus tickets for as little as 5,000 points Round Trip, on distances less than 1,250 miles, so that includes NYC-Fort Lauderdale for example.
The RT tickets are available on select dates in the year. For the remainder of this year, you can get them from April 27-May 25; Sep 8-Oct 5; Nov 2-16; and Dec 1-14.
You can also arrive in Fll, and depart from Orlando, for example.
Taxes and fees on the tickets are only $5-$20, if booked 21 days in advance. (Within 21 days it's $75 just like Delta or others)
You can also get another 10,000 points (2 more RT FLIGHTS) on balance transfers.
Get complementary membership in the $9 club by using your credit card each month.
You can have others fly with your points, if you so desire.
I recently checked a dozen dates, and they had bonus flights available EVERY DAY, during the aforementioned dates. I spoke to 2 different representatives and personally went through date after date, and every date I asked had some availabitity. Some had all flights available, but all dates had at least one flight available. Confused by the many doubters here who have questioned availability, I finally asked the rep, to please tell me which date in May or September is NOT available, and his immediate reply was, that there is no such a thing, as every date was available. I say so, after having 16k points in my account, and actually having them believe that I was ready to book the ticket right away.
So, if the above dates work for you, it mat be quite a good deal