Finding a way for a strong design and user experience culture to develop in open source software communities could be one of the more critical challenges for open source projects to address if they are to remain sustainable or, better still, go close to meeting their incredible & exciting potential.
Since around August last year I've been working with the Mark Boulton Design & the Drupal open source community to make some pretty fundamental changes to the design and user experience firstly of the Drupal.org website and now to the user interface for the upcoming release of Drupal 7.