The Financial Times claims that, like the work by Reinhart and Rogoff on debt and growth, Piketty's research on changes in inequality over time is also beset by computational errors. Though the theoretical component of Piketty's book has been controversial but as the article says, the critics have still praised the historical research. The biggest differences seem to be in estimates of wealth inequality in Britain in recent decades. The data the FT correspondent provides shows no increase in concentration in wealth in the top 1% and top 10% in the UK in recent decades. That would weaken Piketty's conclusions overall, but it doesn't seem it destroys them. Piketty's response is here.