In Preview we have the option both for pictures and PDFs to either chose one pixel being a screen pixel or 100% being resolution independent.
Finally we got back to be able to measure sizes on screen, as a throwback to the times of 72 dpi-screens.
[crarko adds: The actual preference setting reads 'Size on screen equals size on printout.' I only see this in Preview but it's a good step to putting it in the OS as a whole.]

