I was going to say that OS X is basically built upon a Unix base but you seem to have grasped that. What is interesting is that people are talking about Google OS as more of a rival to Microsoft and Windows rather than Apple and OS X.
I personally think a new OS is going to really struggle to crack into the Operating System market, as Apple and Microsoft have such a huge history in this field and both corporations have massive user and fan bases. That being said, I think if anyone is up to the huge challenge, it may well be Google. They certainly seem to have been practicing quite a bit with their multitude of web apps and frameworks such as Signal or whatever it's called.
Competition is always good, but I can't see myself being torn away from my beloved OS X personally. Might take a quick gander though - if I gave Windows 7 a look it only seems to fair to see what the search engine boys have been up tp.