Several leading scholars of administrative and environmental law have raised questions about Sunstein's views on cost-benefit analysis in connection with his nomination to be "Regulatory Czar" for Obama:  their report is here.  One of the authors is my former colleague, and one of the nation's leading progressive voices in administrative and environmental law, Thomas O. McGarity, Jr. of the University of Texas. 

UPDATE:  My current colleague Eric Posner (Chicago) responds to some of the criticisms of Sunstein's work.