I wanted to propose using the new VS 11 Portable libraries to enable a single instance of the CommonServiceLocator to work with .NET 4, SL4+, WP7.1+, WinRT and XBox 360.
The only breaking change is that IServiceProvider has been removed from WinRT and so isn't available for portable libraries. From an API perspective, in my test build, I simply moved the single GetService method to the IServiceLocator interface instead.
Between using it as a Portable Library and the removal of IServiceProivder, the changes would warrant a version bump to 2.0 to prevent accidental conflicts. If you can get that built and put on to NuGet, it would enable you to have a single binary that all platforms can reference.