I left a regional captain gig for Spirit and I haven't looked back. Most of the guys in my new hire class were regional captains as well. Yes the first year pay sucks and you're going to get into some CC debt to maintain any semblance of your regional captain lifestyle unless you have a good chunk of change saved up.
No it isn't Delta, United, or American and I was well aware of that coming into it but the QOL is night and day different compared to a regional. I'm home more on reserve than I was as a senior line holder at my old regional. The trips are easier, the legs are longer, the hotels are much nicer in better locations. There is a huge amount of soft pay available if you're willing to be flexible with scheduling and you can almost always manipulate your schedule to get whatever days off you need. There really is no comparison when comparing it to a regional. Now with all that being said there is still a huge amount of room for improvement with this contract we are negotiating. Especially in pay. And myself and everyone I fly with is demanding a contract that brings us up to our mainline and other airbus peers. So I do believe that it will get better in the future but until I see it I'll still have my applications out at the majors.
I'd rather be stuck here at Spirit if anything happens or I do anything stupid than at my old regional. But to each their own and everyone has their reasons.