I agree that an MBA does not make you necessarily a good manager, as I said in my post, managers need skills and knowledge that an MBA can (hopefully) help to develop. If they are not there to start with, it will not help much.
I also agree that some of the qualities that make a good engineer also make a bad manager. But there are other qualities which are common to both, like the ability to look at problems, analize them, propose alternative courses of action, choose a solution, test it implement it and follow it up.
I understand many of you snuf at MBAs, probably due to bad experiences with people who have one, I have had my share of them.
On the other hand, MBA is a tool. It theaches very useful skills, the financial and managerial knowledge is great and it gives a different and richer perspective at work. It will not make you better than anybody else and it is not a ticket to instant CEO, but it is certainly worth the money, time and effort. At least it was for me, and I would like to think I am not a bigger ass than before I did it.