It's not just "overhyped BSD", the Finder and "Quartz" form the basis of Apple's proprietary user interface. As we know, the choice of "shell" or GUI is still a big source of arguments among users.
If BSD were as easy to setup and use as Mac OS X, Apple wouldn't be selling as many machines as they do. Part of that ease comes from the fact that Apple supplies all the hardware and drivers, creating a seamless installation for the user. Yes, Apple might "crumble" under the weight of having to support lots of different combinations of hardware with drivers written by so many different people.
There is nothing wrong with tying your software to hardware you sell, if that's the terms under which it's licensed it. You get the same thing with Symbian OS or Windows Mobile on a smart phone, you can run that OS only on the hardware you purchased/license it with. Microsoft and Symbian/Nokia will give you no help or support trying to install that OS onto another device and may sue you for license violation if you do.
I do wish Apple would make their machines more user upgradable (e.g. use socketed CPUs and include BIOS support for a significant number of CPUs so I could easily/reliably upgrade the CPU in a machine. I can upgrade the RAM, HD, optical drive, video card, keyboard, and mouse on most systems, but I'm generally limited to the CPUs Apple offers even if better ones are available that are electrically compatible. It's a minor complaint, but....