On this computer (Windows XP SP3, IE 8) I can drag the "slider" up or down, roll the mouse wheel up or down, use the up/down arrow buttons above & below the "slider" and on the Keyboard -- all of which work in both directions.
Point being...with the slider, you move the slider-down...the page goes up. I want to have the page go down. Like if you "grab" the page and move it down.
Like I said...the scroll-wheel to me makes sense. The slider is like a "joy-stick" and to my thinking should be programmable to a particular mindset (not their's).
Way back, some designer said, "this is how it should be!". And I just don't agree and never have.
Brings to mind flying a radio-controlled airplane -- when flying inverted, up-stick is down and down-stick is up -- when the plane is flying toward you, left and right-stick are reversed.
I agree that provision should be made in the driver options to allow user discretion.