This is one awesome feature of climing stairs in bare feet, especially if they are stone. Normally climbing in shoes results in a continual foot tapping sound as you climb. But in bare feet that sound vanishes and, assuming you keep the knees bent and move subtly, results in a silent assent.
Thus the options for sneeking up on some other unsuspecting climber is opened up. I've had fun trying to go up two floors past someone in the middle without them noticing. Tricky but a good feeling when acchieved.
Decent seems slightly harder to keep quiet as every time you have the weight of your body landing on each step. When I get the technique I'll post it.