I had a Retina MacBook Pro with Windows 8 already installed. I can boot from it without problems, and all the drivers Apple provided for Windows 7 works perfectly for me except one thing.
I am not able to use Target Display Mode with a Thunderbolt iMac. I understand that Boot Camp doesn't currently support Windows 8, but I am hoping someone has encountered this problem and solved it.
Also, I am able to connect to an HDMI or Mini Display Port-equipped display under Windows, and Target Display Mode works under OS X.
Best Answer
Target Display mode is not supported under Boot Camp for any version of Windows, the best way to get that working is under a VM client suh as Parallels or VMWare