been great when factoring in price.

I would never fly spirit on one of those cross country flights. However, I did fly from LA to Cabo on Spirit and it was only $79. That was a two hour flight and I was at my limit on those seats. But at $79, a quick weekend in Cabo becomes totally doable.

Like you said, the catch is that you can't bring luggage. Once you ad a bag, it starts to get close enough to the other airlines that it becomes a more questionable proposition.