However, it's really easy to install pretty much anything you want via the ports or packages systems, and the cool thing about them is they integrate into the system very smoothly. FreeBSD gives you a very minimalist base install-you pretty much get a C compiler, a couple of shells, vi, and that's about it. In terms of the base installation, they're actually very different. If you're comfortable with one UNIX, picking up a different one may require learning some new tricks, but it's not going to be terribly difficult. Installing software isn't that different. The important files are (more or less) in the same places, most of the functionality is in principle the same (though it may have different names and work slightly differently on various platforms, but it all pretty much does the same stuff).
That's also true of Linux and most UNIX and UNIX-like operating systems. As far as the UNIX experience goes, there's not really that much difference between OS X and FreeBSD.
