Misc. forenote: not sure if true on all systems but on mine, if you right-click on the scroll bar it acts similar to the old scrollbar arrows (in my file manager it's slower, but moving the mouse speeds it up)
My eyesight is not the best (and my screen isn't that big), but I still don't mind it (for example Firefox). I like that it doesn't seem to change content width (even expanded, it's still in the margins with my higher zoom level). Though I could see using a brighter scroll bar, particularly as it gets smaller (also, a darker scrollbar background to increase contrast). Color might help for readability too.
Back when I used Chrome I didn't like the white scrollbar background and light-gray bar that was horrible contrast yet too bright (and in the corner of my eye it didn't register properly due to that). At one point I used an extension to fix that with a thinner-but-high-contrast bar.
Then again, I also made my own ultra-compact window theme for XFCE (well, XFWM). Frameless and the titlebar is 12px tall but the window buttons are only 8px tall... some of the buttons are slightly wider to compensate (minimize and maximize are widest at 20px), though I would ideally like to allow them to be wider with a wider window (with the current setup, a long-titled window will be made shorter if the buttons take up too much space on a small window).
There is some utility for this as well, as I can have a small music player on-screen or even rolled up and it doesn't block much on the screen. Though I admit it's diminishing returns, specifically without making my own WM which I am unlikely to do.