Fantastic news. This has been a major issue for the development team to which I belong, so we are very much looking forward to this.
It sounds like this supports full "server" .NET, the client profile, the metro profile, Silverlight, phone, and XBox. There's at least one other .NET-based platform that doesn't seem to have received much love recently (but got a really quick mention in this video): .NET Compact. The company I work for has TONS (as in many, many thousands) of rugged mobile devices that run Windows Mobile 5 and more recently, Windows Embedded Handheld 6.5. These devices have to last for many, many years (upwards of 7). But the .NET version is still stuck at 3.5, and the development tools still stuck at VS2008.
Given that Windows Mobile is still supported and sold on new devices today, and that Windows Embedded Handheld still seems to be a current, supported platform, I would hope there are plans in place to bring .NET Compact to a current level (v4.0 or even v4.5), to support rugged device development in Visual Studio 11, and to add support for .NET Compact to the Portable Library Tools. We would love to share code between our ASP.NET apps, Silverlight apps, and .NET Compact apps but we can't due to lack of support in VS2010, and the lack of support in Portable Library Tools.
But still -- overall great news and great progress in the right direction!