Following up on yesterday's post: My W10 SP2 played a shuffle of my music collection, continuously, for 7' 55". That's significantly greater than under 8.1 Media Center (which ran the same as regular 8.1) -33 to 40% more, if not better. The power setting is Balanced, with 15" screen and 30" sleep times. The playback went into screen dimming several times, but only for brief moments, and into sleep once. It never stopped playing. This simple battery-time test indicates an impressive improvement, now more like my 8.1 RT's times. Video playback is my next test, to see how it compares with my Kindle and RT tablets. With even greater improvements in start-up and shut-down times, and a faster browser, however, this SP2 has already become a very efficient machine. And there's a big update coming... Good work, Microsoft.
Edit: the SP2 auto-shut-down at 7% battery level. I wasn't watching the screen, but I wasn't expecting it. Low-battery pop-up warnings came at 10 and 7%. While it didn't shut down right when I closed the 7% warning, when I re-started, plugged in, the level was at 7%.