My opinion is different: The regionals suck. I came from one of the "good" ones and Spirit is still definitely better. Once you're on second year pay there's no comparison. The flying, schedules, and airplane alone are so much better. Flying an A320 between major cities is so much better than flying a junk E145 to Peoria. I'm actually realizing that I wasn't truly happy during my regional years. I'm on 4th year pay and make over $100k working a leisurely schedule, generally flying on the days I want and to the destinations I like (west coast). I *might* hold captain on the bid that closes tomorrow. We also have the jetBlue merger to look forward to (which I think will be a big improvement over the current state of affairs).
As for the idea of staying at a regional until a legacy calls, I think that's now a farce. I recently interviewed at my choice legacy. In my interview group of 8, there were ZERO regional pilots. Not one. Surprisingly there was only 1 military. Everyone was ULCC, ACMI, or 135. Another Spirit pilot I spoke to recently interviewed at a different legacy. 20 in his group. Only 5 were regional, all check airman. Not a single one got an offer. All the rest were hired (10 military, 5 other). The legacies don't want to hire from the regionals. It hurts their ability to fly the RJs. They want to hire from places like Spirit. So if you did want to go to a legacy, going to Spirit and getting the A320 type is possibly the best pathway.
I'm actually still unsure if I'll take the legacy offer or just stay and enjoy being (eventually) jetBlue. I live local to NYC and when the integration is done I should be able to hold JFK captain on any plane.