I took a few classes at UM while getting my MBA at another university a few years ago.
My observations are that it's a beautiful facility with engaged faculty and good students. Relatively low student to faculty ratio makes learning more interactive than in other big state universities. Even at the Graduate level, some masters level classes have 70 students in them. That really just makes them glorified undergrad classes (but the students still pay grad level prices for them!!) That's the advantage that you have with private schools like UM, although you definitely have to pay for it!
My broader critique consist of the actual academic content of the program, which are really common to all MBA programs. While the technical knowledge, especially in the accounting programs, are top notch, finance seems to be somewhat shortsighted. The focus is on managing risk rather than preventing it. Since then, I've come to realize how so many of these MBA's up in Wall Street managed to miss the glaring signs that there was a broader systemic problem lurking in the financial system. Analysis among most academics within the field is very short term and myopic. Marketing courses are interesting, and I find the UM program to be particularly strong here. I consider management courses to be overly theoretical and pie in the sky. Way too much positivist ideology for my tastes. Business Law, Economics, and Ethics usually round out the curricula.
I don't think the value of an MBA is as high as it was a few years ago: the market is already drenched with people possessing the degree and the economic downturn has put a crunch on job and internship opportunities. Also I think the curriculum needs to be readjusted, particularly in the field of finance, to reflect the new realities within the market. It is definitely a worthwhile degree, but I would balance it out by taking an undergrad degree in the humanities or the social sciences. That type of education provides historical context, which is really missing in the MBA.