With SharePoint Server 2010 Enterprise edition, what additional benefits do I get using SQL Server 2012 Enterprise edition as opposed to SQL Server 2008 R2 Enterprise edition?
From a database perspective I think the improved High Availabilty features are the main point.
From a SharePoint point of view the better integration of PowerPivot and Reporting Services are the main things.
And then you have the longer support time as an extra bonus.
But you can go through MSDNs What's New in SQL Server 2012 to look for things which are important to your company/use.