I have talked to people who have been to fancy MBA programs. The ones who had (substantial, management-related) work experience first say that they already had learned everything the university could teach them. The ones that did it right out of school said that they didn't really understand what the university was saying until they saw it for themselves in the field. These were non-technical MBAs that taught accounting concepts and management strategies (as opposed to these modern MBAs that have a lot of statistics courses), so I'm not sure how closely this aligns with the situation today.