Job dissatisfaction is what ultimately led me to the FIRE community. I stumbled into a position that pays extremely well. So well that I can live a very non-Mustachian life and still save well over 50% of my take-home pay. But it comes at the cost of extremely inflexible 60-hour work weeks, living in a city I'd rather not, and a general discouraging trend in the work itself.
Prior to learning about FIRE, I just assumed I'd be working until age 65; and that contributing to 401(k) and having an emergency fund was good enough. I feel like my biggest struggle now is basically hedonistic adaptation. For ten years, I've lived only according to "basic" personal finance principles: spend less than you make, no consumer debt, etc. Fortunately, we never went too crazy with the spending (no McMansion or luxury cars), but we picked up a lot of small luxuries and "premium" lifestyle habits.
What's frustrating to me is that, had I realized FIRE was a possibility five years ago, I'd probably be writing my own ERE/MMM style blog right now, rather than being a complainypants about my first-world problems. :)
I don't know if that adds anything to the conversation, but I just thought I'd throw it out there. To answer the initial question: the FI goal hasn't changed the outlook on my job so much as it has just about every other aspect of my life. Reading Your Money or Your Life, and sites like ERE/MMM that build and expand on those ideas has made me realize that my life is less pre-determined than I originally thought it was. Or, at least it's opened my eyes to ideas I don't think I would have come up with on my own.
Though previously I haven't actually lived the belief, I know there are plenty of people who are as happy or happier than I am, but have substantially less means. It's always been this kind of romantic notion. But I like how MMM has basically framed it as a practical, optimal lifestyle. That appeals more to my action-oriented intellectual side than my daydreaming romantic side. I have to make the change in myself, and "sell" it to my wife at the same time.