When Visual Studio 2012 came out, one thing was sorely missing. An Expression Blend tool that can handle WPF 4.5 applications. Blend for Visual Studio that is currently available only supports Windows 8 Store Apps, but not WPF (or Silverlight).
A few days ago, Microsoft released a preview of Blend 5 (with Sketchflow), that’s able to work with WPF and Silverlight, along with Windows 8 Store apps.
The tool can be downloaded from here: http://www.microsoft.com/en-us/download/details.aspx?id=30702
Microsoft stated that the final version of the tool will be available with Update 2 of Visual Studio 2012 (Update 1 was released about 2 weeks ago).