For a quick overview let me tell you that I have WSUS 3.0 SP2 on a Windows Server 2003 Std Ed. which has been recently upgraded with the KB2734608.
The only problem I see is that at the WSUS server I can see my Windows 8 and Windows Server 2012 clients, but if I run the WSUS console (mmc... add/remove snap in...Update Services...Connect to server), it doesn't show my current operative system on clients,
it displays Widnows XP Professional x64 Edition for Windows 8 and Widnows Server 2003 Datacenter x64 Edition for my Windows Server 2012 clients.
This forum is for System Center Essentials(SCE) related issues. However, I'm afraid this question is only related with WSUS. If so, please use the following Forum, which would be the best resource in your scenario.