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

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 time writing?
Do I get floating windows and docking, like in Visual Studio 2008? Is there a money-cost to using it?
What does the deployment look like - is my app a standalone EXE, or is it shipped as some sort of one-off package or archive that runs within the shell?
Is Eclipse RCP a good comparable, and if so, how do they compare?

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.

Visual Studio Shell enables developers to rapidly create and distribute their own custom tools by building on a streamlined Visual Studio IDE.

A Visual Studio isolated shell-based application has full access to Visual Studio services and supports customization and branding. There are several ways you can customize a shell-based application, as follows:

• You can use add-ins and VSPackages to extend an isolated shell-based application just as you would use them to extend Visual Studio itself.
• To make Visual Studio features and menu command groups available or unavailable, update the .vsct file in the user interface (UI) project of the application.
• To remove Options pages or other Visual Studio shell components from the application, update the .pkgundef file of the application.
• To modify other aspects of the appearance or behavior of the shell, update the .pkgdef file of the application.
• Some aspects of the shell can also be specified when the application is started. To do this, update the parameters in the call to the Start entry point of the appenvstub.dll.

The Visual Studio Shell is freely available as part of the Visual Studio SDK. Visual Studio Shell is royalty-free for building and deploying applications.

Your isolated shell application can be installed on any computer that has the Visual Studio 2008 Shell (isolated mode) Redistributable Package.

Each isolated Shell-based application to be deployed must have a valid shell load key (SLK). The SLK is uniquely related to the application and cannot be used to load any other application. You can obtain SLKs on the Visual Studio Extensibility Developer Center Web site.

After you obtain a shell load key (SLK), you must add it to your Shell project. Follow this procedure to add an SLK to a project that was created by using the Visual Studio Shell Isolated template.

Note: Everything said up to this point has been copied and pasted from various Microsoft documentation pages. A good place to start might be Walkthrough: A Basic Isolated Shell Application.

I used the integrated shell to try IronPython at home, without having to install the full VisualStudio trial version. It's a nice IDE if you're used to it.

It seems there is a big difference between the integrated shell and the isolated one.

The integrated shell is an IDE without any programming language installed. If you don't have VisualStudio but want to use a free plugin such as Python Tools for Visual Studio, then you can use the integrated shell.

The isolated shell is well described in Powerlord's answer, it seems to be made for programming software developpers, since it allows branding and modifications of the user interface.

Seems like if you use the stand-alone shell, you could build your product in a way such that it could plug in to Visual Studio. Then, you could distribute your product as a stand-alone with the VS shell), or as an add in to Visual Studio. (just a guess)

I realized I'm late to the party on this, but back in the day when Sybase released versions 12 and 12.5 of PowerBuilder, they included a .NET version of each product. It was PowerBuilder running in the Visual Studio Isolated Shell. Honestly if you ask me, they did an outstanding job on it. The only drawback was that it was initially focused on generating WPF targets, assemblies, etc. But you couldn't do WinForm development (within PowerBuilder .NET). You had to deploy that through the PowerBuilder Classic interface.

Recently I've been getting into some Python and I remembered that one of the groups had also developed a Python deployment using the isolated shell. But I can't seem to find anything additional on it.

Granted, I realize that Python can be written in Visual Studio now, but just was trying to dig into the history. I noticed last night when I was digging that the isolated shell is available all the way through 2015.

Does anybody know if it has been discontinued?