I randomly happened upon this blog, which I found to be an interesting and well-written account of leaving academia. The author talks very honestly about some regrets, and how the long investment in a PhD wasn’t necessarily directly useful.
I am now five years out of my tenure track position. I have zero–zero–question that I did the right thing in leaving, but I do daily have misgivings about whether I left for the right thing. I have an academic degree and not a professional one–in my field, it is pretty hard–there is no straightforward career path once you leave. You have to find your own way somehow. Everybody finds a different way.