Dennis Miller is one of my favorites. He's easily one of the most intelligent comics out there and has perhaps the greatest mastery of the language, and has an amazing font of knowledge from which to draw his wonderful analogies.
That some people don't understand him doesn't mean he's using words horribly or has bad grammar. He's just being him and you've really got to be on your toes to keep up.
That said, my dad hates him because he's "too snotty". I've never heard anyone accuse him of traits belying lack of intelligence before though.