I don't know if this is known yet but I have come across one thing that prevents Widi from working for me.
Internet Connection Sharing. If this is enabled on any of the network adapters then the Widi connection will fail. I am using the Intel Widi 4.2 application on Windows 8.1. (The built in Windows 8.1 method still does not work either way).
When Internet Connection Sharing is enabled the Widi application will attempt to connect but it fails after entering the pin. My Samsung TV display will a "connected" message but the connection fails after that. Normally it will begin showing the desktop after the connected message but instead it exits AllShare mode. The Intel Widi application appears as though it is connected for a few seconds but it fails and shows the error message saying to restart the application.