… is having a better idea of what’s going on.
- It isn’t about making more money.
- It isn’t about becoming entrepreneurial.
No. It’s about having a reasonable idea of the whole business, rather than just the specific function. 
I don’t think the MBA made me "entrepreneurial." I do think that it made being entrepreneurial easier, because as I struck out on my own, I had at least a general idea of the various functions, and what was supposed to happen. I didn’t have to guess what the buzzwords meant. The knowledge was enabling.
More money? Maybe, more likely if it’s one of the top few schools, but even there, a good opportunity costs analysis usually shows that people are not better off, on pure money terms, quitting good jobs to go back to school for two years.
More entrepreneurial? I doubt it. It’s easy to argue that another two years of schooling is the opposite of entrepreneurial. And also that the qualities of entrepreneurship are hard to teach.
A better view of the bigger picture is an extremely well made argument. Do you have any links to the opportunity cost analysis for b-school that you speak of in your second to last paragraph?
@Casey, yes, try this google search. It turns up half a dozen items doing the opportunity cost analysis. I guess I should have included that in the post.