What do you think of Ben Bernanke as Chairman of the Federal Reserve?

If not Bernanke, who you would rather see in that position? Do you think the market meltdown and credit crisis falls at his feet, or do you think that it really began with Alan Greenspan and the 1% rates during 2004 that allowed too easy credit when economic conditions really did not warrant it? What about the roles of Congress/Bush administration (SEC, Treasury, House and Senate oversight committees)?