As most SharePoint 2010 developers know, you cannot normally create a Visual Web Part "project" that supports sandboxed solutions.
Instead, in Visual Studio 2010, you have to create an Empty SharePoint project as a sandboxed solution and then using the SharePoint Power Tools you can add the Visual Web Part Item Template for sandboxed solutions.
Well, while this solution is an "OK" workaround, it is definitely not very appealing and certainly requires more time and effort than simply having this template out of the box.
Fortunately, Visual Studio 2012 now offers the Visual Web Part as a project template!! Therefore, you can just create the Visual Web Part project as a sandboxed solution in Visual Studio 2012 and you are ready to go!
Well, what if you do your production development with Visual Studio 2010?? Never fear, now that Visual Studio 2012 has backwards project compatibility with Visual Studio 2010 SP1, you can simply open the resultant project and solution file directly in Visual Studio 2010!!
What a great deal!!