I've worked on WP, Joomla, Mambo, and a few others and the one thing that they all lack is some commented notes in the CSS to help designers style the Fonts, layout, and colors. Often these CSS files can be very long and trying to find elements that you would like to style can be a very time consuming process and frustrating. I've spent hours on themes changing css and previewing to see what's been changed. I think if developers spent a little more time commenting important styling elements designers would be eternally grateful and flock to your themes. Just an Idea!