gswitcherd is launched by systemd and gswitcher is launched gnome-session-manager. All fine.
If gswitcherd detects a connected HDMI port on boot it tries to turn on the discrete card (effectively turning off the integrated). Sadly there is currently a bug (or so) in vgaswitcheroo which prevents the successful switching from one to another card between plymouth and gdm. Maybe this will be fixed at some point - or not be needed at all ...
Another problem is about looking up the HDMI status (to automagically detect what card to use). This is just possible if the discrete card is powered on, but this ain't the case when we are using the integrated card. The current solution is to power on the discrete card once and again, to determine the HDMI status.
Beside all problems gswitcher will notify you about a freshly connected monitor and will ask you to log out (and back in).