Check it out, the LightSwitch team just posted another Channel 9 video. In this one we go a little deeper into how to customize screens and extend LightSwitch. We also talk a little bit about the architecture on which LightSwitch applications are built:

In this interview with Joe Binder, a Program Manager on the LightSwitch team, we discuss the LightSwitch application framework architecture and how a LightSwitch application is built on top of well-known technologies like Silverlight, MVVM, RIA Services, and Entity Framework. Joe shows us how to modify the behavior of a screen and how it exposes the commanding pattern in an easy-to-use way. He also shows us how to extend the UI with our own custom Silverlight controls, as well as how to connect our own data sources using RIA Services.

Channel 9 Interview: Visual Studio LightSwitch - Beyond the Basics

If you missed it, for an introduction to LightSwitch please see this interview as well:
Jay Schmelzer: Introducing Visual Studio LightSwitch

For more information on LightSwitch, please head on over to the Visual Studio LightSwitch Developer Center and please feel free to ask questions in the Visual Studio LightSwitch Forums.

Enjoy!