Merely pressing Super alone and releasing it will show all your Windows now. In addition, also the keyboard shortcuts Super+s and Alt+F1 will show the window overview.
Changing the shortcut combinations to show the window spread
If you wish, you can set it to Super+w by changing the assignment of "Show the overview" in Settings - Keyboard. That, however, will replace the second shortcut Alt+F1 and leave the Super+s shortcut in place. If you want full control on what key combination or combinations are assigned to that function, you can change the dconf setting org.gnome.desktop.wm.keybindings
. For example, to set both Super+w and Alt+F1, you could change the key using dconf-config-editor
or with a terminal command:
gsettings set org.gnome.desktop.wm.keybindings panel-main-menu ['<Super>w','<Alt>F1']
To reset to default:
gsettings reset org.gnome.desktop.wm.keybindings
As to why the change?
Ubuntu used to have its own in-house developed desktop, Unity. With version 17.10, they moved to the Gnome Shell desktop, where Super alone, Super+s and Alt+F1. So with respect to these hotkeys, they decided to adhere to the conventions used in Gnome Shell rather than trying to continue their previous choices in the Unity desktop.