The girlish voice was a little unnecessary... That, and the hair comment. Because we all know that politicians are equally superficial in relation to fashion choices (and not necessarily by choice, seeing as there is an institutionalized way of dress in politics), so the comment comes off as sexist.
God, this fucker annoys me (I'm talking about Williams, and not [immediately] Letterman). You can see him clinching his brain-waves so hard to be 'funny,' and brings up every 'joke' with a smug, self-satisfied smile (see any Daily Show interview for expiation and fortification). Two stars because the metaphor was nearly engaging.
Three-stars, but I agree. Brian Williams is funny by virtue of the fact that he can identify funny jokes when they are said by not-him and grin at the camera accordingly.