The Nvidia driver fails (I've tried 367, 364, 361) when I attach a monitor to the mini displayport. As soon as I do that, the UI changes... I think Unity fails to load given all the fonts change, icons, window borders, etc, plus the monitor is not recognized - I can't even start the Screen Display setting application. Now, if I unplug the secondary monitor an reboot, my Unity is back again. Also note, if I run the Intel Power Save Prime profile, my secondary monitor is recognized and works just fine.
I'm on a Dell 7510 with the Quadro M1000M GPU.