I installed Windows 10 on 7/31/15 and the PI 1.8.3 migrated from my Windows 7 installation just fine. In fact most of my old apps work as well or better than under Windows 7 with Windows 10.
However.... When I uninstalled PI 1.8.3 and installed 1.8.4, I couldn't find it in the Start menu or the All Apps menu. I could go to the Programs folder and pin it to the Task bar, but I couldn't pin it to Start, where I wanted it. I don't think this is a PI problem, because I tried uninstalling PI 1.8.4 and re-installing PI 1.8.3, and I had the same problems just mentioned for PI 1.8.4. I've also read on Microsoft Fora that other users are having the same problem. PI 1.8.4 is currently running on my Windows 10 machine, everything links to it, but I can't use it from the Start Menu.