Call me supremely lazy, but I use the spacebar all the time (Thinkpad), since my thumb already rests on it and it's so big that I can't miss it. I even prefer it over scrolling.
Page-Down means I have to almost move my hand away from the keyboard (middle finger to the top right corner, can't hit it with other fingers because display) -- that feels like grabbing for the mouse...
Page-Down means I have to almost move my hand away from the keyboard (middle finger to the top right corner, can't hit it with other fingers because display) -- that feels like grabbing for the mouse...