We are upgrading a data warehouse to 2012 at this very moment because...we are almost in production (june) and I'd rather bite the smaller impact of regression testing now prior to production than the much larger impact afterwards, we are already running beta 2012 MDM due to the limitations of the 2008R2 MDM, and I expect we will make use of many of the latest features such as DQS and significant SSIS improvements.