I use Linux on the desktop and I haven't touched an X11 configuration file in many years. I would have to Google for its location if I wanted to even look at it. Stuff just works now - except we don't have intelligent multimonitor support (until now).
The GNOME 3 "Displays" app is pretty good. You can toggle mirrored, external screen to the left or right by just dragging, etc. It isn't quite as slick as the one shown in the video, but it's certainly functional and easy to use.
KDE has the same thing, but it's not smart at all. It will pick the wrong resolution for the wrong screen, if I disconnect a screen the windows that were on it become inaccessible, it never remembers my setup when I re-dock the laptop, and so on.
It depends. For example if you use Nvidia driver and tools - they offer good and convenient multimonitor support out of the box. Without Nvidia it's quite messy, I agree.
