Apple have updated the Human Interface Guidelines for Leopard. When I say updated, I mean it’s more like an act of necromancy. The HIG was largely neglected during Tiger times, with a great job being done by the Indie HIG, though that hasn’t been updated in a while.
The idea of a unified interface still appeals and Apple have got closer with Leopard, but is there a need for uniformity? With the web everywhere and each site having it’s own style, it’s obvious that a lack of uniformity isn’t hampering usability. People aren’t stupid, they know what a button is.
A lot of what’s in the HIG could be just as well served in SDK documentation, the HIG itself could easily be summed up as a guide line that makes developers and UI designers simply ask ‘Is this simple and beautiful?’
Sadly Apple has a problem complying with the HIG itself…
Make sure you do not change the behavior of standard elements. When you need a new behavior, design a new element for it.
Which hardly explains the behaviour of hierarchal folders in the dock since Leopard. At least give us a preference we can change.