We flew spirit a week ago Sunday, the beginning of all the "weather" delays. Inspired by this thread, I purchased the Capitol One travel insurance for $40 a seat. And yes, the savings with bags and all were still super significant over any other airline.
When our flight got delayed, we weren't concerned because we could rebook on any airline through Cap1. We ended up sticking it out, took off just 2 hours late, and got our flights refunded through the insurance.