I think you know my story, so I'll try to be brief.

First degree was a BA in Sociology and I spent 7-8 years in retail management. Quit at 30, started bartending and had no idea what was next. I was single, debt free and had the freedom to decide. I ended up with a BSEE and an MSEE in a highly specialized field (that has been booming in recent years). I worked as an engineer for 8 years and then struggled with my choice. I *almost* went back to school for veterinary medicine (at 43) but landed my current job instead. Currently I am the college program manager for my company. I am a liaison between the technical and the non-technical in a hi-tech industry. I like that I get to combine skill sets from both previous careers into one...for now.

I expected that this job would be short-lived when I took it. I mean, I could stay where I am until I retire, but I don't really have the desire to do that. My plan is to work in this role for another couple of years (to finish creating this program and to make myself obsolete so that I can move on to something else). As I plan for this, getting an MBA is high on my list of possibilities for my next step. I hesitate not because of my age (45 now) or any fear of the academic challenges, but because of finances. When we sold our farm last year, the plan was for us to retire in about 10 years (at 55) and farm again. If I do an MBA that'll shift our finances quite a bit and might require us to delay retirement. I need to decide if it is worth it at this point in my career. Will the MBA do that much for me or not? I'm in the research stage of this decision right now.

Anyway, my advice is to really weigh the options. When it comes to a full on career change (like I did at 30), it was 100% worth it. No question about it. BUT (and it's a pretty big BUT), make absolutely sure you are choosing the new career for the right reasons. I don't think I did and there was a time there where regret was pretty dang high. What are the right reasons? I can't say. The wrong ones are really any reason that stems from your dissatisfaction with your current career/job. Don't let what you don't like now influence your future. Choose your path based on what you truly want to do, not on what you want to avoid.

To answer some of your questions:

Why did I do it? I saw no future in my job at the time and I really wanted a totally different career path.
Would I do it again? Yes - but I might have made some different choices. Timing was right, the impulse was right, but my decision-making algorithm was wrong. No regrets now though as it has all worked out for the best.
What was the hardest part? Living as a broke student after having been fairly 'well-off'. This is the biggest hurdle for me about business school, too.

Sometimes it's important to feel the fear and do it anyway.