I single boot Linux on my 13" MBP retina. I use xmonad+xfce and it can be tuned to work reasonably well with Hi-DPI. There are still some things that don't work great (chrome), but it certainly can be done.
My big problem is that there is no support for different DPI settings for multiple monitors. This is quite unfortunate and keeps me from using the full resolution on the laptop's display. Right now I run the laptop display at 1680x1050 (still quite a bit higher than the non-retina 13"), which plays nicely with my 27" monitor at 2560x1440.
Besides the display issues, Linux runs great on the MBP retina (late 2013 MacBookPro11,1). Things run more smoothly than my last Macbook (a mid 2010 13" MacBookPro7,1) which had occasional wifi and suspend/resume nvidia issues. The only thing that I can think of that doesn't work is the builtin webcam, which was switched from USB to PCI-E and doesn't have a linux driver yet.