Exposé is just the squeeze-buttons on my mighty mouse
Front Row, the menu button on the remote control...
Spaces...I don't have Leopard, but nevertheless I wouldn't need the icons because the shortcuts are so easy
in leopard i use the front row and spaces icons in my dock as i find them it easier and quicker to click on instead of the keyboard shortcuts. but i have no use for the exposé icon as i have it set for my scroll ball on my mighty mouse. haha its so useful and i often find myself clicking the scroller on and windows pc and expecting the windows to "expose".