I agree that aesthetics is definitely important to an interface, many people (most notable "artists") feel stress when having to interact with an ugly or messy program (like an old version of cakewalk or logic platinum) and more at ease with pretty and functional programs (like ableton live or reason) ... it definitely isn't the most important consideration, but it matters.
For clarity, I'm not trying to call PD ugly or messy, I actually am quite fond of its clean look. I do think that little subtleties of design go a long way though.
-Josh