The game works swimmingly regardless of what input device I use. Afternoon phase becomes less cumbersome to navigate with the mouse, especially as more locations get unlocked. Also, name entry is less annoying to perform with the mouse than with the keyboard. Which sounds odd, but one must remember that the name entry screen does not take direct input from the keyboard.
The keyboard isn't totally useless, though. If the only thing one can do during School Phase is choose between "Move", "Wait", I'm not seeing many people use the mouse for that. On a similar vein, I'm not seeing many people use the mouse for decisions that have only two, maybe three, available options.