I've booked two tickets on F9 TPA-DEN-TPA in January. $49 each way, $196 for two RT (plus $100 for a checked bag for each of us, round trip). No connections to worry about in January. Can't beat it.
My primary concern is that a lot of the endless series of 1* reviews on Yelp (almost all of which seem to be from people who didn't read what they were buying when the bought the ticket) mention extremely long lines for checking bags at DEN. We have a 6:30 AM flight from DEN-TPA. How early do I need to get there to check bags and still make the 45 minute cut off?