I posted a comment over at Five community challenges for design in Drupal 7 & beyond. It is awaiting moderation but here it is in case it doesn't get approved.

@Mathieu – saying that coding is fundamentally about rolling out features and bug fixes is like saying that design is rolling out sizing boxes and picking color schemes. To bring any design to life, there are a number of choices that have to be made when it comes time to implement them in code (both front-end and back-end code). And, although choices are deeply individual, we’ve found ways to come to a consensus and make group decisions.

For Designers who think there work ends with producing a PSD or other mockup, the issue queue + IRC are not going to fit their work habits. Neither will having to defend most of their decisions after they have been made. I think designers have a tough job there, because good design is holistic. The Open Source community is used to testing and challenging proposed solutions, so designers might feel like their precious creations get unduly criticized when shared. Also, Drupal needs to be flexible to fit different use cases, so trying to have a one-true-solution is impossible.