Even when dedicated interface designers are present, they are not heeded as much as they would be in professional projects, precisely because they’re dedicated designers and don’t have patches to implement their suggestions.
from Why Free Software usability tends to suck

This is an excellent point!

I am less enthusiastic about one of his later points:

Many hackers assume that whatever Microsoft or Apple do is good design, when this is frequently not the case. In imitating the designs of these companies, volunteer projects repeat their mistakes, and ensure that they can never have a better design than the proprietary alternative.

I think it is more often the case that many hackers miss the nuances in what Apple or Microsoft does and so end up with a UI that superficially resembles that of a similar Apple or Microsoft product, but doesn’t work nearly as well.

I suppose this is another danger of imitation, that you don’t understand the reasoning behind the component you are copying and so might miss important subtleties.

But then there is this:

many contributors to a volunteer project want to be rewarded with their own fifteen pixels of fame in the interface

Fifteen Pixels of Fame!!! I love it!