Though I am a very frequent flyer, today is my first time flying with Spirit, and even out of Terminal 3. It has been a good experience, so far! My flight is on time, the plane staff is funny and the Sri Lankan lady who checked me in was super sweet and helpful.
Spirit Airlines is one of many airlines that only charges you for the services you actually need. That's one great thing about them if you travel light, like I do. If you like to check in at the airport instead of at home, check or take -on luggage, choose your seat or board early, understand that you'll be paying extra for it. I'm just glad they give me the option to decline those services instead of writing them into a higher ticket price. That's why I call these airlines "a large carte " carriers. :-)
I'd recommend Spirit Airlines to friends and would take them again myself.
BTW, terminal 3 only has a Starbucks, Wendy's And Mexican place for food so plan ahead of those don't sound good to you!
See ya there!