Well, flying as an air courier 3 times in the early 90s with just a carry-on for a 2-week Asia trip was good preparation for flying Spirit. Have been to Cancun for 5 days and San Jose C.R. for 5 days with just the rucksack that's the maximum you can carry without paying. Would be harder to pull off to a cold-weather destination (maybe just wear all your clothes layers)

Spirit miles also aren't like regular airline miles. Expiration is aggressive unless you have the credit card, and you really need the card to build much quickly. Off-peaks are in narrow windows and go very quickly, so they're seriously over-baiting people by touting them so much. If you can spend 20K+ miles, availability is easier, but then there's no advantage over legacy airlines and you're always subject to the pile of junk fees they have. Avoiding all those is an art in itself and takes maximum flexibility (and it helps to be single, though 2 savvy people also can do it). I use Spirit only for trips I totally wouldn't take otherwise, like maybe $60-ish RT 2-dayers to FLL (sometimes Tuesday-Wednesday!). People with less-flexible arrangements tend to run into the fees more, and those can make it more expensive than regular airlines.

You can carry on a bag that fits under the seat for $0.
carry on bags for overhead bin at time of booking - $35
$9 fare club carry on bag for overhead bin during booking - $25

Sounds like the only reason I'd fly Allegiant.

Sounds more like a scene from one of the Saw films.

Went to the Bunny Ranch, eh? :p

Make sure you get a Big Front Seat™.

Good advice - just checked them out - you are correct -some interesting airport/routes.

This is my rule #2 of Spirit travel. The first is to only fly them on optional trips that can be fully scrubbed without penalty when the plane's 20 hour daily rotation gets delayed and they start cancelling legs to make up time.