Update Rollup 12 just fully released today, but the December 2012 Service Update has been running in some of our CRM Online deployments for several weeks now.  The Microsoft CRM Support team recently posted a blog article with some of the frequently asked questions and known issues for the December 2012 Service Update and Update Rollup 12 (UR12).  Whether you are using CRM Online or preparing to deploy UR12, I recommend that you review this blog.  They are planning to keep updating this post, so if you are not deploying for awhile, check back later for the most recent updates.

https://community.dynamics.com/product/crm/crmtechnical/b/dynamicscrmsupportblog/archive/2013/01/28/december-2012-update-has-been-released.aspx

As always our PFE team is ready to help if you need the assistance.  In addition, we have a plethora of other services we offer such as developer training, admin workshops, and code reviews.  If you would like to have another Microsoft PFE or I visit your company and assist with the ideas presented on our blog, contact your Microsoft Premier Technical Account Manager (TAM) for booking information.  For more information about becoming a Microsoft Premier customer email PremSale@microsoft.com, tell them CRMInTheField or I sent you.

Thanks!
Shawn Dieken

Microsoft Premier Field Engineer