Entity Framework 5 is included in Visual Studio 2012, but is also available to users of Visual Studio 2010 (as a NuGet package: http://nuget.org/packages/EntityFramework/ ).
Note: Some Entity Framework 5 features are only available when writing an application that targets .NET 4.5. This includes enum support, spatial data types, table-valued functions and the performance improvements.
Read more about what is new on the MSDN ADO.NET blog: http://blogs.msdn.com/b/adonet/archive/2012/08/15/ef5-released.aspx
Update [08-27-2012] : Julie Lerman has an excellent post describing the difference between running EF5 in a .NET 4 versus a .NET 4.5 application, read more on: http://thedatafarm.com/blog/data-access/when-entity-framework-5-ef5-is-not-entity-framework-5-ef5/