For those of you that modify or create Visio diagrams using the VSDX file format you will be happy to know that the Open XML Package Editor for Visual Studio has been updated and this release supports the VSDX file format.
Here is a link to the latest release.
http://visualstudiogallery.msdn.microsoft.com/450a00e3-5a7d-4776-be2c-8aa8cec2a75b