David Letterman has totally lost his mind... I've watched Letterman for decades now, and he's always managed to funny, and biting, without going crazy, and without getting nasty.
Even in this election he'd avoided the nastiness, until McCain stiffed him. Since then he has spent almost every night getting really nasty, and very vindictive about McCain, and especially about Palin.
Also, Brian Williams is pretty funny, very smart, and quick on his feet.
Of all the major network anchors (now that Tim Russert has passed on) is the least biased, and most gracious.
I wonder, with Russert and Williams, if their Catholicism (Russert remained until his death, and Williams still is, a very sincere catholic), and specifically the Jesuit education they shared; had a big hand in that ability to remain fair and gracious, though both are self identified democrats.