Forum OpenACS Q&A: Is www.edwardtufte.com using OpenACS or an older version?
If so, its a de facto endorsement of the model from a usability perspective.
furfly hosts the site, but all the work on it is done by David Rodriguez, who used to work for Arsdigita. As I recall the site was originally built by Jin.
I was following up on his "sparklines", as a useful approach to providing at a glance business intelligence data, and happened to glance at the url.
Its a very clean interface (to be expected), and an interesting site!