The scroll bar numbers make me further believe that OS X Lion's scroll bars are a bad design. My computer is not a tablet... saving ~10 of 1920 pixels is not something I needed or wanted.
I have turned my scrollbars back on, not because I want to use them, but because I want to look and see how much of a page is left without moving my mouse over there. I never actually click on it.
What jumped out at me was the 71% for the reload button. Unless they've changed the layout since I customized my copy, the reload button defaults to being a tiny button at the right end of the awesome bar. I moved mine to where Chrome has it and these numbers indicate that a lot of others have done the same. That or Mozilla moved it and I naturally didn't notice.
Ubuntu Unity has some neat tricks to make scrollbars more usable [1]. Instead of requiring users to hone in on the up/down arrows or the "thumb", hovering anywhere near the scrollbar brings up a widget that compactly encapsulates all this functionality. I don't care for Unity enough to start using it day to day, but this feature struck me as clever though radical.
Aha perhaps it wasn't so obvious from the videos I viewed. I did notice that a few people were quite desperate to turn off the unity scroll bar while on my travels looking.
I'd recommend avoiding scrolling as much as you can. I prefer myself to page with the space bar - well at least on web pages. It's much nicer. (Shift and Space to go back up.)
Scrolling is tiring, in that it requires me having to do a lot of eye tracking.
I notice this all the time with your 'normal' user. The scroll bar is quite possibly the most horrific unfriendly control. It's just too narrow. Those users that don't have that much control of a pointer, struggle with scroll bars and small buttons / drop downs etc.
I like the Apple way of placing controls on the left, but having a scroll bar on the right negates a lot of the benefit of doing so.
Having said that they are quite handy as page length / where you are indicators.
