A lot of us actually use multiple Unixen and view the notion that MacOS is one too to be laughable.
It's more UNIX-like under the surface of the UI than any modern Linux distro I can think of personally. A lot of us actively manage REAL UNIX boxes as well and think you're full of crap.
The major difference is the fact that it doesn't use a dated clusterf**k of a GUI environment and has actually evolved since the 80's instead of piling kludge on top of kludge to mimic functionality found in other more high-performance GUI environments.
Would OSX be my SERVER environment of choice? Probably not. But as far as UNIX WORKSTATIONS with real desktop software go, OSX is lightyears ahead of anything Linux or FreeBSD have to offer. Or any commercial UNIX vendor for that matter.
OSX is quite a bit less f**ked up than Solaris. And OSX is the most widely used UNIX desktop environment on the planet. And I'm glad it doesn't use the GNU userland, I prefer BSD anyway. If you want OSX to be more traditionally UNIXy, install MacPorts, XCode, XQuartz and TotalTerminal. And go tick some checkboxes in various preferences in Finder and such to make it work as you expect.
You bash OSX yet every modern FOSS desktop tries to mimic it terribly and cram Windows-like UI elements in as well. And the Linux crowd is doing its best lately to try to make Linux as un-UNIX-like as possible to the point where it's becoming difficult for a desktop environment to even properly compile and run under FreeBSD anymore which is far closer to real UNIX than modern Linux.