[GFischer]

But they´re the wrong lessons if you want to do a startup... an MBA is very focused on an existing firm.

That´s why Paul Graham et al advise against it. There´s some very useful knowledge, especially financial and accounting and knowing organizational dynamics if you want to go B2B (not to mention connections).

I personally sometimes regret spending the money and effort on my master´s (a Tech MBA). It definitely didn´t give me the career advancement I was hoping for.