Personally I find it is incredibly helpful to be able to see the scrollbar at all times, even if I primarily use a mouse scroll wheel, trackpad gesture, or keyb

Personally I find it is incredibly helpful to be able to see the scrollbar at all times, even if I primarily use a mouse scroll wheel, trackpad gesture, or keyboard for scrolling. The slight bit of horizontal screen space it takes in every window is a trivial cost in comparison to the value of knowing how tall the scroll is and where the viewing window is currently scrolled. (Note, it is also more effective to grab the scroller and drag it along the track vs. using other mouse/keyboard gestures in cases where the scroll is extremely tall or wide – anything more than about 20x the window size – and you want to move precisely to one particular part. I find this especially helpful when reading books or other long documents.) I wish user interface designers looked for more ways to provide unobtrusive extra information in parts of the screen I am not otherwise using.