Bradford de Long sums it up this way:  (1) the return on wealth varies inversely with the wealth-to-annual-income ratio so strongly that, paradoxically, the more wealth the rich have, the lower their share of total income. Thus, their economic, political, and sociocultural influence is weaker as well.  (2) Not bound to the karmic wheel of earning, getting, and spending on necessities and conveniences the rich can take the long and/or heterodox view of things and create, say, great art. Ie, the sculptor R. Seward Johnson  and tenor and music teacher Paul Sperry  (both heirs).  (3) A new industrial revolution that will create more low-hanging fruit for the masses to pick and become rich.  (4) The limits of the data [Piketty] presents and the grandiosity of the conclusions he draws…borders on schizophrenia.  (5) The George W. Bush argument: Piketty is French and so….

Disagreements with Piketty focus on different 10-20 %s of his arguments and overall he is being accepted by everyone.