It's not so much the "random power-ups" as it is the high current demand of actually taking a picture. If you're using alkalines and they start showing low battery, you can actually swap them for another set; after they've had a few hours to "rest", you'll be able to resume using them. But alkalines are designed for a steady current draw, like they'll get in a flashlight, radio or MP3 player. When they are asked to put out high current levels in very short times, they rapidly run down. NiMH cells and lithium disposables are better able to handle "burst" demands and so will last longer in that type of use. One way to look at it is to think of alkalines as distance runners while the NiMH cells and lithiums are sprinters. Your average (or even world-class) marathoner woudn't do as well in the 100 m dash as someone who specializes in that because the demands are different.