I think Chris talked about Starkers in his "Designing for WP" series.
But ya, I’ve used Starkers. Love it.
I’ve also used the sandbox (http://sndbx.org), which uses alot of complicated php to give posts and pages dynamic classes that describe the post’s date, category, tag, author, etc.
I like Starkers more tho, its more flexible, clean, and simple under the hood.