I read that the display on the epic does not use any power to display blacks or whites.
No power for blacks, but 3X the power for whites. AMOLED achieves true blacks by turning off pixels, but whites require them to be full on.
If the SAMOLED screen devices primarily displayed black text on white background, they would end up with lower battery life than LCD screen devices. It doesn't matter for LCD screen devices since the backlight is on regardless of the colors on screen (which is also why they can't achieve true blacks).
If you have a SAMOLED device and spend a lot of time on websites, ereaders, or messaging apps with white backgrounds, your battery will drain very quickly.