WordPress developer Jacob Santos on WordPress Child Themes: WordPress Theme Modifications should be made in Child Themes.
If you want more of an introduction to theming your blog or website with WordPress Child Themes you can read my two-part interview with Weblog Tool Collections’ Jeff Chandler on the subject. Part One gives an introduction to the concept with a ridiculously easy tutorial that guides you through making your own Child Theme. Part Two goes through some of the business implications of using them with a WordPress Theme Framework.
Pat Dryburgh outlines the drawbacks to child themes—which hinder public acceptance and experimentation—that he’s discovered while working with Thematic.
Darren Hoyt explains why he’s interested in WordPress Child Themes in Exploring WordPress Frameworks and Child Themes. He does a great job illustrating why professional designers using WordPress to power sites need to take a serious look at them.
Elliot Jay Stocks has updated and re-released his WordPress starter theme, Starkers.
Alister Cameron has written a simple function you can add to any WordPress theme that lets you intelligently and automatically force browsers to use your updated WordPress stylesheet.
Are premium themes open source? Should they even exist? Read When Premium WordPress themes and open source ethics collide for a good, controversial take on the subject.