The quote I like is "The only intuitive interface is the nipple, every other one has to be learned"

So as long as an interface is consistent with prior interfaces I guess it is "intuitive"

I have never used mac, but it sounds like a good interface to me, not the .dmg one, that one is. weird. but where the application is self constrained in it's own directory. The traditional unix method where the parts go according to their function (/bin /lib /share and all the /usr variants) is fine when all the software is system software(promotes reuse) and sort of works when you have a sys-admin whose job is to incorporate third-party software as system software(central package systems also fit this category), But it really starts to stink when you have independent third parties packaging their own software.

Another way to think about it is what is the best hierarchy function/application or application/function