articulate and engaging.
This makes his arguments less likely to be valid than equally persuasive arguments from someone inarticulate with no stage presence.
That is a trivial point, since finding a dull speaker persuasive is very unusual. Would you even spend 30 minutes listening to a boring person?
David Deutsch, whose views are very much aligned with the scientific ideas generally advocated on this forum (except for his use of probabilities), and whose new book The Beginning of Infinity has been recently published, talks about many of the topics of interest to LW. (A flash player might be needed to listen.)
While I find his case for the MWI weak (he mostly says that it explains what we observe better, without going into predictive power or Bayesian reasoning), he is, nonetheless, quite articulate and engaging.