This is exactly what I've been waiting for. The OnMac wiki has the specifics of getting triple boot running. If necessary, using OS Xs Disk Utility, adjust the sizes of your partitions, making room for Linux. Unfortunately, swap files tend to run slower than do swap partitions, so if you're running multiple Linux applications on a Triple Boot Mac, you can expect to see a performance hit. This is a tried and true way of getting around this kind of problem. If you want to start up using the default operating system now, click Restart. Select the startup disk that has the default operating system you want to use. If a User Account Control dialog appears, click Yes. You can get around this by using a swap file instead. In Windows on your Mac, click in the right side of the taskbar, click the Boot Camp icon, then choose Boot Camp Control Panel. That leaves one for each operating system, but Linux needs two partitions - one for the operating system itself, the other for the swap partition. Apple reserves the first primary partition for its bootloader.
It's definitely clear that Apple's Intel Macs are an extremely valuable commodity to the computer enthusiast, letting you run every OS under the sun.
Unlike the Boot Camp method of installation, some advanced tinkering around with chainloading Linux's lilo bootloader from the XP ntldr bootloader is required. If some features arent working when you start your Mac from Windows 10, try reinstalling Boot Camp support software using Boot Camp Assistant. A recent discovery from the people that were able to get Windows booting on an Intel Mac before Apple came along with Boot Camp allows you to triple boot with Linux.
When Apple released Boot Camp, they made it easy for anyone to dual-boot their Intel Mac with OS X and Windows.