Something to keep in mind: the MBA wasn't intended for entrepreneurs...way back when it originally was created it was designed for major corporations, like GE and GM, who needed professional managers. Business schools and MBAs are designed to produce them.
I'm not going to say that an MBA is useless, but it serves a specific purpose...and that purpose is not to foster creativity and entrepreneurship.
Like Dave has suggested in the past, there's a need for some sort of EBA--entrepreneur business school. Steve Blank also talks about this idea...his point of view is that the E-School (as opposed to B-School) should be attached to the engineering department (as opposed to the business department).
Here's a link to Steve Blank: http://steveblank.com/2010/05/10/entrepreneurial-finishing-s...