This is an interesting take on style, typesetting, publishing, and CSS. I don’t agree with all of it but there are some nice ideas here and the page/approach is very nice looking.
The main thing I disagree with is Tufte’s strong preference for text and prose rather than lists. I think this is highly dependent on a person’s individual taste. Also I’m not convinced that a person who’s scanning an email message or document will absorb a paragraph of prose as well as a bullet list.