I have installed funtoo on my 2013 Macbook Air. It took a few extra steps like manually adding an entry into refind.conf which I found here http://croutchie.blogspot.com/2012/12/how-to-install-refind-bootloader-in.html and adopted to my own needs. So far so good. The main problem is broadcom wifi but that is easily fixed if you have an ethernet cord or other source of connecting and emerging broadcom-sta. Other than that I have had zero issues.