Just to mention it, there was some issue reported with Windows 8.0/2012. The symptom was that customization would get stuck when applied to a just cloned VM which not powered on before customization.
I've seen it all the time in multiple environments, you had to trigger the scheduled task created to run the customization either manually or through a reboot after template deployment and initial power-on. Anyways, this issue was fixed in vCenter 5.1 U1 already: VMware KB: Guest OS customization of Windows 8 and Windows Server 2012 may not complete
On the topic of vCD support: I don't think vCD has to "support" Guest OSes directly and I know of no such matrix/compatibility list. If the ESXi hosts and vCenter, which are directly interacting with the guest OS, support it, then vCD is covered as it merely hooks into vCenter APIs.