Re: Power efficiency difference
One would expect an OLED panel to more efficient than LED if it was displaying a mostly black image - indeed, this is one of the reasons Samsung is pushing a dark themed UI. LCD screens are backlit as a whole and dark pixels are blocked, whereas OLED screens only light up pixels when required.
The surprise here is that Apple's OLED solution uses more power than its LCDs even when displaying dark images. This is apparently due to the controlling circuitry Apple use, not the actual panel.
As for who needs that level of colour accuracy, there are a few trades and professions that benefit from it. Whilst a screen is no substitute for a colour swatch, it can only aid some workflows if the screen gives a better approximation. Historically, Apple may owe their survival in the 90s to Macs use in the DTP trade - at a time that DOS and Windows PCs couldn't be colour calibrated as reliably. It might also be argued that the original Macintosh didn't *need* a GUI, but since it had the required hardware it was then easier to develop DTP software.
This said, DisplayMate say the Apple specced (Samsung made) OLED is only a smidge better than the Samsung phones that previously wore the crown.