Exactly - and I don't think OS X was ever truly a microkernel, it used Mach as the base for XNU, but it was always a hybrid kernel even going back as far as the

Exactly - and I don't think OS X was ever truly a microkernel, it used Mach as the base for XNU, but it was always a hybrid kernel even going back as far as the NeXTStep days. Well, it uses it now. (But yes, not as a microkernel.) You never know how something will come handy — learnt Hurd programming => now not afraid of Mac OS X kernel'ish stuff