On the MacOS, scrollbar sliders for large lists aren't allowed to grow shorter than a set minimum size (below which it's hard to click on the slider with the mouse.) Current gtk doesn't do this, and from the gtkbeta preview shipped with RH7.1, it doesn't seem current gtk2 is fixed. IMO, this is a serious usability issue.
GTK does do this - the size is just small currently. GTK2.0 also has this, in fact the range can be set in your gtkrc file (theme)