[devnull3]

> a visually appealing GUI

I think it requires a combination of things: a good taste, a sense of visual design and programming. The first two is more of art form.

Most of the developers on these projects are really good at programming but its rare to get a good combination mentioned above AND willing to work on open source over multiple years consistently.

Update: Also someone in the decision making hierarchy needs to have a keen sense of design. Example: Steve Jobs learnt calligraphy and even though he did not actually designed it he would certainly veto and pass feedback to the developers.