Announcing Internet Explorer Developer Channel
The really amazing thing here is that they've disentangled IE from the base Windows. The key comment:  This release of the IE Developer Channel uses a combination of code changes
  and App-V Client to virtualize and run alongside IE11.

This is pretty huge, because it means that the support requirements for IE can be drastically reduced. That means faster releases without harming backwards compatibility. One IE for the server and OS platform, one IE the application platform (modern apps), and another for the user. Or even instanced per-user IE, or who knows what they could do. It's a big deal that they've gotten IE to the point that it can run in an App-V container, and the result will be a faster development cycle and earlier access to new features in the client, without imposing a huge support matrix on application developers.This could pan out into versioned webview controls and all sorts of things. I hope Microsoft is willing to take this as far as it can go.