I've found Kegan's work to be an extremely useful lens on the world, and I've found his research with Lisa Lahey to be extremely useful both for my personal development and for my company. We currently have a pilot program implementing insights from their books An Everyone Culture: Becoming a Deliberately Developmental Organization (one of the best books I've read in years, and I read a lot) and Immunity to Change, and I think it's made a significant difference for those who are taking part in the pilot and for the company in general.