http://blogs.technet.com/b/configmgrteam/archive/2014/03/24/configuration-manager-servicing-update.aspx
Great post, I know questions around this come up all the time. The last paragraph is a keeper. >From a servicing perspective, consider System Center 2012 Configuration >Manager SP1 and System Center 2012 R2 Configuration Manager as two separate >products. In other words there is no dependency between SP1 CUs and R2 CUs, >and SP1 CUs are not a prerequisite for R2 CUs. There may be issues common to >both SP1 and R2, and if so we will document any fixes as needed. Daniel Ratliff The information transmitted is intended only for the person or entity to which it is addressed and may contain CONFIDENTIAL material. If you receive this material/information in error, please contact the sender and delete or destroy the material/information.

