What is the Visual Studio shell (standalone shell) good for?

Question

Is it some sort of pre-built GUI scaffolding?
Why would I Want it instead of a WinForms UI, which is quick to set up?
What does it give me that I would have to spend

Answer 1

I would like to mention that SQL Server Management Studio 2012 requires both of these entries in Add/Remove programs:

1. Microsoft Visual Studio 2010 Shell (Isolated) - ENU
2. Visual Studio 2010 Prerequisites - English

I know this because I uninstalled them, broke SSMS, and had to repair from the installation media, upon which those 2 items reappeared.