> How do you know when there is content to scroll then? You randomly scroll parts of the screen to see if they move?

Sometimes, but more often I press on page down to read more content until there's no more content to read, so having scrollbar is pointless: it eats screen real estate without providing anything in return

I loathe things "magically" disappearing and reappearing. I want a predictable, consistent interface. I can work faster when things are consistent. Scrollbars, besides allowing me to jump around in a document, give me an indication of where I am on the page. When I ask, "How much of this page/window/document is left? About where am I in it?" (a common question) the answer should be RIGHT THERE and not unhelpfully hidden/unavailable or difficult to see. I shouldn't have to waste time fighting to find out.

> I loathe things "magically" disappearing and reappearing. I want a predictable, consistent interface.

I do not want the trackbar to magically disappear. I want it gone for good, unless I ask for it, which is predictable and consistent.

> I can work faster when things are consistent. Scrollbars, besides allowing me to jump around in a document, give me an indication of where I am on the page.

I work faster with a good concentration, which is helped by a lack of UI clutter (FYI I use my browser in fullscreen mode because I find buttons and tabs distracting)

Hitting the touchscreen, doing a gesture on the trackpad (or the trackpoint), or pressing pageup then pagedown gives me context when I need it and if I need it.

The rest of time, I don't want no scrollbar.

> When I ask, "How much of this page/window/document is left? About where am I in it?" (a common question) the answer should be RIGHT THERE and not unhelpfully hidden/unavailable or difficult to see. I shouldn't have to waste time fighting to find out.

When I do any of the above, the scrollbar is here. The rest of the time, I shouldn't have to waste my concentration on a useless indicator nagging me on the right side of the screen.