Been using them the past few months flying to St Pete airport. No friils airline, and it is a direct flight. Round trip for around $100 or less. I don't check in luggage, I have clothes and stuff at the gf's house in FL. I don't even have a carry on bag. I don't choose my seat, which makes it even cheaper.
Only downside is, they only fly Tuesdays, Thursdays and Sundays. And only to certain airports. It works for me. But they only have certain flight times.
It's limited, but if you can work around it, it's fine.