On a retina display (3200x1800) E is not behaving consistently.
Elements that do not scale according to configure scale:
- desktop switcher
- arrows in menus indicating sub-menus
- text of desktop notification bubble
- checkboxes / radioboxes
Backgrounds (of desktop and desklock) do not scale up properly (for desktop background switching to a different virtual desktop and back fixes it - outside area being drawn in white -- for desklock no other virtual desktop to switch to and outside area remains transparent).
If needed I can demonstrate at FOSDEM.