Mac Gurus are geeks. Any Mac Guru worth their capital "G" would have explored Linux by now as a diversion and form of entertainment.
Linux is not a bad operating system. It is mostly just very unpolished, but not much worse than trying to use Windows. A lot of the same UI schemes are used in Linux, making it easier for Windows users to transition to Linux than for Mac users, and non-guru Mac users don't need Linux. The Unix underpinnings of Mac OS X are sufficient for most open source purposes.
Linux is only really polished as a server operating system, and there it is very slick and feature rich. Linux will never be anything but a bitplayer as a desktop OS, but I'm not sure why it needs to be a desktop OS.