On the broader questions of Piketty's book, I recommend the reviews of other parasitic critics, including Larry Summers, Paul Krugman, Robert Solow, and James Galbraith. I think the best single review is that of Branko Milanovic, which I link to in my post. The blogs of Brad Delong (Equitable Growth) and Tyler Cowen and Alex Tabarrok(Marginal Revolution) have both featured ongoing discussions of the book, with links to many other commentators.
I find Piketty's analysis very compelling for trends of high-income countries, particularly the United States. As I try to say in my post, I think there is tremendous uncertainty for any long-term forecast of worldwide growth. I am extremely interested in the question of top income shares in developing countries, but I think we don't yet know much, and more work is needed.