Seems to be my bad. I've got some extra patches that aren't in 3.6 to make this EFI stub booting thing work (not that the actual graphics switching works for me at the moment). They can be downloaded here: http://people.canonical.com/~sforshee/apple-gmux-patches/ However, I've been just rebasing them in my git tree for a while so I don't know if they cleanly apply.