I have similar problem here! I use testing with evdev, nvidia proprietary drivers, and multseat. My system start, gdm are started too, but I couldn't log in because my mouse and my kbd isn't work. I need to login by ssh and halt the system. I have another problem too: my system only start after a lots of trying. The system crash after grub start and before udev populate the /dev -- Marcelo Luiz de Laia