It also works almost flawlessly out of the box on the Retina MacBook Pro. The only thing that requires adding is the Broadcom b43 modules and possibly the proprietary nVidia drivers.
Yes, it defaults to full retina resolution (2880x1800). Although it doesn't look too bad like that, and Ubuntu let's you modify the UI font size, I'd probably run at a more reasonable 1920x1200.
Very impressive.