Via M-x all-things-emacs, an Emacs feature I've always wanted and has been there all along: navigating between windows using cursor keys.

(windmove-default-keybindings)

Shift + a cursor key moves to the window in that direction from the current window. You can change the modifier from Shift with an argument to this function:

(windmove-default-keybindings 'meta)

Or you can pick your own key bindings for the windmove-* functions, where * is up, down, left or right.

I am never typing C-x o again.