Michael Fields posted on the theme review team listserve this morning that the WordPress.com Theme Team has created a resource page for theme guidelines. They use this resource for reviewing themes submitted to WordPress.com, but it can be useful to the theme review team, and your own themes, as well. Thanks theme wranglers!
edit: I missed Michael’s post on Theme Shaper about this. A good place to go for more info!Read more @developer.wordpress.com