Great thread. Lots of food for thought.
After a couple of decades in IT, I moved into the videogames industry. If I thought IT was dysfunctional, boy howdy did I not know I was hopping from frying pan into fire.
When I didn't have FU money, I stayed in a couple of toxic jobs in IT. When I finally did have it, I used it not only to leave two really toxic jobs (and managers), but to tell them, professionally and clearly, exactly what I thought of them and why I was leaving. The second job was my dream job, too; I would still be there had I not had a horrible, self-serving manager who had no experience of reasonable business practice outside the games industry.
For me, leaving those jobs was almost as brutal as being in them. The FU money did not give me a sense of pride and accomplishment when I left; I was physically ill and miserable for a long time. Was it me, was I just not employable, would I never find a good job, etc. What the FU money did give me was an exit and time to recuperate.
And yeah. People leave managers, not jobs. The jobs, I liked fine. The managers, not so much.
Now I have a really great job. I love the work, the people, my team, and my manager. I also love knowing that if anyone tries to push me around, I can just saunter out the door and never come back. Because you never know; it's a volatile industry, and people move around all the time. My coworkers' desks are covered with knick-knacks and toys; mine has almost nothing personal, and no more stuff than I can take home in a single box.
So FU money didn't give me any awesome exit stories, but it does give me more confidence and freedom from worry about the future, which lets me enjoy my work even more. It also lets me take jobs I really want even if they don't pay well. Funny thing, though -- when my current company wanted to transition me from contractor to permanent employee, my FU money put me in a position to risk asking for a higher salary to compensate for the pay cut I'd taken when I took the job to begin with. And I got it.
So my FU money led to higher income too. :)