When I was at the Media Lab <mumble> years ago, his group was perceived internally as one of the top groups, and everyone I knew who worked in his group had great things to say about him.
pcl, out of curiosity, what group was that? I was under the impression he didn't have his own particular group. Just that he oversaw other groups. Could be wrong though...
I only ever worked down in the basement, and visited via the corporate sponsorship avenues, so I'm just repeating what I've heard. Have never worked with him directly.