I am running w8.1 on a Lenovo Flex 15 laptop. After about 20 hours of troubleshooting drivers, reloading from Lenovo / Intel, etc. I finally decided to troubleshoot my firewall. I disabled the ESET Family Security firewall temporarily and voila! instant WIDI connection. I had to allow Outbound access to c:\windows\system32\WUDFHOST.EXE and inbound access to a system component I didn't write down. This is a bit of a chore with ESET. There may be an easier way but I used the PERSONAL FIREWALL | FILTERING MODE | INTERACTIVE MODE to figure out which items were being trapped by the firewall for the WIDI app. All firewalls do this differently, but with ESET once you identify the program or system function when it Pops Up you can then instruct ESET to create a permanent rule and select ALLOW.
Anyway, I also had run the Intel Update Tool 2.0 before doing this. So now I have the latest drivers and WIDI is working flawlessly. I did have to play around with the SOUND settings in Control Panel to get audio working correctly, I had to make the WIDI Speakers the DEFAULT speakers for Windows, then the audio also worked properly. The audio took about 10 minutes to figure out. I'd think that there's a better way to get the audio working, but I couldn't figure it out.