Note: This is tested with MacBookAir 11" 5,1 and eOS Freya Beta1. Some of the issues you may encounter can be solved by looking at the rest of the "Ubuntu" base installs and fixes.
For those who want to give it a shot, the preparation should be the same as with this link: http://sudo-science.com/dual-boot-mac-os-x-and-ubuntu-14-04-on-macbook-pro-retina/
With my setup, I split the 120GB 50/50... The 50 is configured as "Free Space" in Yosemite's Disk Utility. After installing the rEFInd, you'll be able to boot in your Live eOS Freya.
In the partitioning process, I did create the "swap" partition first, I assigned 8GB for it, just to be sure. Then created the "/" as EXT4. Those are the only two partition i created for eOS.
After successful install, you'll be able to see that everything is working, including the Keyboard Backlight, Brightness Control, Wireless, Bluetooth and also Suspend/Wake Up.
You will notice that the fans will be screaming after install. To be able to fix that, I installed the following:
- macfanctld * Manages the Fan
> sudo apt-get install laptop-mode-tools macfanctld powertop
rEFInd is a bit slow at boot up, but for me it's OK. I am still able to use Yosemite in Dual-Boot.
I haven't benchmarked the battery yet. But it'll be bias because I use this laptop differently as per everyone else.