In terms of Linux on the mid-2012 Retina MacBook Pro, I have tried Ubuntu 12.04 LTS, recent Ubuntu 12.10 development snapshots, and various other Linux distributions. With no Linux distribution tested was there any reasonably sane experience for end-users with the rMBP. When trying to boot Ubuntu 12.10 and other Linux distributions via USB, there would be no display and nothing appeared to work -- after looking closer, it looked to be a kernel panic. To work around this first hurdle, noapic needs to be set from the boot loader as a kernel command-line argument in order to get the kernel booting on the Retina MacBook Pro. The noapic option disables Intel's Advanced Programmable Interrupt Controller, which with the Linux 3.5 kernel still seems to be hitting problems for this new Apple laptop.
When booting up after the kernel tweak, the display was trashed:
Yep, even the open-source Intel Linux graphics aren't working right with the Retina MacBook Pro hardware. If rebooting the system and using nomodeset in addition to noapic, at least the display will properly light up and we can proceed to the Linux desktop... However, that's without Intel kernel mode-setting and thus no 3D acceleration support.
At the Ubuntu 12.10 desktop, sound worked, the web camera worked, but the WiFi was broken. When proceeding with the Ubuntu installation, the EFI boot-loader installation had gone awry so reFIT had to be used for booting the Ubuntu 12.10 development installation on the Retina MacBook Pro. After the Ubuntu 12.10 installation and trying an early development build of the Linux 3.6 kernel that shared the same problems as found on Linux 3.5 and earlier.
For getting the WiFi to work on the Retina MacBook Pro, the b43 firmware had to be manually installed on the system from the Broadcom driver and using the b43-fwcutter. Of course, doing this could be a problem unless you happen to have a working Thunderbolt Ethernet network adapter or are using USB to transfer all the necessary files over to the new Linux installation.