Improving the Cappuccino Theme System
annema.meI think using JavaScript to parse CSS is a great solution to this. Even as a developer I find theming with CSS easier than Objective-C-style code.
The fluid nature of HTML is fantastic as well. Insert a div and the other stuff moves to make way for the new element. Remove it and things pop back. That sort of thing is a major PITA with standard Cocoa views.