I definitely agree that Linux has come a long way in Linux support, with my monitor now been plug and play, not plug -> terminal -> configure a few settings -> restart X -> play
The usability issues come when you plug in something, expecting it to work, only to find that you need to fire up the manuals, for example function keys in LXDE. Gnome had come a long way, until they went to Gnome 3 , but Gnome Shell Extensions are getting us back, problem is that a new user should have an idea of what Gnome shell Extensions offer without having to read up.
In a perfect usable systems, users should not have to read the manual