Our domain consists of a wide array of operating systems including XP, Windows 7, Windows 8, Server 2003, Server 2008 and/or Server 2008 R2. Is there a preferred Group Policy Management Console I should be using?
Yes. You should always use the latest and greatest GPMC. As of this writing, thats the GPMC on Windows 8, but the Windows 7 one is just fine too. (Note: You will get more settings and features if you use the Windows 8, or Server 2012 version.)