Another post on the Windows Phone blog from a couple of weeks ago talking about the uptake of Unity as a development platform on both Windows and Windows Phone.

http://blogs.windows.com/windows_phone/b/wpdev/archive/2013/11/18/1000-unity-apps-across-windows-store-and-windows-phone.aspx

And a good video introducing Unity development for Windows Phone.

http://channel9.msdn.com/Shows/Inside+Windows+Phone/IWP50-Introducing-Unity-for-Windows-Phone-Devleopment