He gave a talk on Evolution of Mutation Rates, a topic many of us treat with a large degree of skepticism—until we're confronted by Michael Lynch. He makes a convincing case for variable rates of mutation in different species and he challenged us (me) to defend the idea that there was a linkage between DNA replication rates and mutation rates. That's a linkage I've always assumed would constrain mutation rates to a narrow range. Now I'm not so sure.
Lynch's paper is here.