What is the Visual Studio 2008 Shell?

You might be aware that many third-party tools integrate already today into the Visual Studio IDE, such as products from Borland and Compuware. Now, with the forth-coming Visual Studio 2008, Microsoft is taking the integration possibilities even further with the introduction of the Visual Studio Shell.

From the page: "Visual Studio Shell provides the core foundation so you can focus on building your application’s unique features. Flexible customization options help you deliver optimized experiences for specific markets."

Sounds very good to me, except that if for example CodeGear would choose to go this route with their Windows IDEs, then that would be more or less the end to the IDE competition.