Hunting for design guidelines, I found the Gnome styleguide to be rather detailed whereas the iPhone HCI styleguide(1) remains quite general.
I was looking for advice how to use colours (I’ll blog about this soon) – and some (official) thoughts about when to use premade widgets and when to use custom ones.
(1) Due to Apple’s rather esoteric communication policy, you need to register to see the webpage. Call me a coward, but I won’t mirror the pdf.