TimesSquared - I think we may be saying the same thing in different ways. I thought Stewart was his usual amazing, immediate, funny/tragic self, and got as much from the role as possible. It's just the play itself is not very "dramatic." The dullest audience knows there are times in Shakespeare where something extraordinary must happen - "To be or not to be" or "Tomorrow and tomorrow..." Mamet is so good at capturing ordinary speech that the actors don't have any heightened language where a star turn is expected by the audience - except perhaps that dreadful/wonderful parody of a speech at the barricades.
"that dreadful/wonderful parody of a speech at the barricades."
Funny, I didn't find it wonderful at all. I found it trite and tired. It's been done a million times already. So too the autumn leaves, and practically everything else in the play. It wasn't fresh, and it wasn't funny.