Microsoft has released a hotfix (12.0.2504) which includes two fixes.

• KB #2999809 : FIX: Poor performance when a query contains table joins in SQL Server 2014 – this actually has to do with segment elimination in clustered columnstore indexes.
• KB #3058512 : FIX: Unpivot Transformation task changes null to zero or empty strings in SSIS 2014 – this KB actually has the single download package that contains both fixes.

My advice is to install this hofix only if you are using SSIS with Unpivot or clustered columnstore indexes. Do not hold out for the Service Pack 1 re-release, as these fixes are highly unlikely to be included there. For more information, see this post.