How I did it... I have an OS X Yosemite VM for VMWare... I created the installer using Unibeast and a spare external USB drive. Tossed in a 320GB HD I have into my desktop, installed Yosemite on it. After the install, it would still just boot to Windows 7 on my SSD so what I did was boot off the USB installer and told it to boot my Hackintosh install, which worked and got me to the desktop. From there, I ran Multibeast, a tool that installs kexts, drivers and bootloaders for your Hackintosh. Everything works for me, including USB 3.0 which is pretty good.
It’s a bit of a pain, having set up Hackintosh before... but this was by far the easiest time. The motherboard is an ASRock Extreme3 Z77 by the way.
If I boot my desktop, it’ll still go straight to 7 unless I tell BIOS to boot off the 320GB HD which will automatically boot Yosemite. That’s exactly the way I want it.