Was going to book a trip from Philly to Myrtle Beach on this airline because they are cheap, but the copious scathing reviews online scared me away.  Specifically concerned with late and cancelled flights that seem to be the norm.

I've used them a several times without issue

same

You get what you pay for.

I've used them and been alright. The seats are cramped. I believe they are the ones that charge $100 at the door for carry on's if you don't reserve one ahead of time. I lived.

There was a guy at my work that flew Spirit a couple times a month. I don't know the backstory, but the guy is marrying a girl in TX with two kids so he would fly out there a couple times a month to spend time with them. Sprit allows a "personal bag" of some sort (like a purse) for free but charges for any carry-ons, etc. So he would pack a backpack with a couple sets of clothes/toiletries and be good to go for the weekend. He never had any issues and I believe they started flying out of Sky Harbor now. He always had good things to say about the place.

My only other knowledge of them is that they ran a $69 deal to celebrate their 69th plane. Love a company that doesn't care about being PC.