Hmm.. I'd certainly agree that the BSDs are more 'pure' unix than Linux is, but OS X and iOS are very much adapted derivatives, not pure at all. 
Agreed, actually. OS/X is certainly recognisable as Unix under the skin. Driven from the terminal command line most of the unix utilities are there, and (if you know unix) then it's nice to see the filestore laid out in a unix-like fashion.
But then again the slightest task, such as opening a new browser window, often leads to the appearance of the dreaded spinning colour wheel and commencement of mysterious and endless disk thrashing before, several minutes later, the machine eventually becomes usable again. No, that's not Unix as I remember it.
