Microsoft has just released Cumulative Update (CU) 3 for ConfigMgr 2012 SP1.
As well as fixing various issues, CU 3 adds support for Windows 8.1 to the supported platform list for Software distribution, Software update management and Compliance Settings.
NOTE: You don’t need to reboot once you’ve applied CU3.
Full details at:
http://support.microsoft.com/kb/2882125
I have added this to the ConfigMgr 2012 KB Articles list as well as adding a link to the Microsoft Downloads page so you have everything in one place.