I am glad to hear Windows 8.1 Preview adds one, which means more than likely it would stay between now & Windows 8.1 General Release.
I am going to download Visual Studio 2013 on my Windows 8.1 Preview machine & start development from there then I think, because the lack of proper controls means a lot of work for me.
I know there are 3rd party ones, but they don't just give me the code or walkthrough how to do it, they have paid options, or downloadable custom controls, where all I want is to program it, I don't need it pre-made.