Mac OS X is more like FreeBSD (UNIX) than Linux.
That said, Macs will also run Windows and Linux natively now (i.e. without an emulator such as VirtualPC), so you're not constrained to OS X if you don't like it.
I'm using a quad-core Woodcrest-based Mac Pro right now, and while I have the option of booting into Windows, I rarely do so (and then, it's only for Battlefield 2 and Microsoft Flight Simulator).