One issue people are finding with the December CTP is that it requires that you choose both Visual C# and Visual C++ when you install the Visual Studio Beta1.
 
If you missed out Visual C++ then you'll get an error message when you finish the wizard that goes something like "The template specified cannot be found."
 
We currently use a Visual C++ project to produce the unmanaged satellite DLL that a VSIP package requires to store its menu items, toolbars and icons.  In a future release we'll be looking into producing an entirely Visual C# based solution.