Just a quick update on this thread:
Since getting my Retina Macbook I've been running OS X pretty successfully with the help of Homebrew
to provide the toolset which OS X cannot. Things like htop, rdiff-backup and nmap are all not on OS X by default and the installation of them using Homebrew is really simple and effective.
I've also created a small 50GB partition to experiment with Linux on the hardware. I've installed rEFIt and have tried daily builds of Xubuntu/Ubuntu Quantal Quetzal to see how well it all works. (I did try Fedora 17, but it died shortly after grub with some error I cannot remember.)
The experience is far from perfect. Booting requires the use of "noacpi" and "nomodeset".
The Broadcom wifi adapter works once you have used b43-fwcutter to install the firmware and modprobe the modules.
I have not been able to get the Nvidia drivers working correctly, although admittedly I haven't spent too much time trying yet.
The good news is that is runs blindingly fast, so once we have all the kinks worked out, it will be a great Linux laptop.
I asked Greg Kroah-Hartman for an update on his trials to get Linux working on it and he responded with a succinct: "no x yet, being worked on.