Last week I was on a 73H with USB and AC power. I didn't try the USB, but used the AC substantially to read documents and type up a report on my laptop, and then play one of the internet games on the gogo homepage for the remainder of the flight. Granted, my laptop had been in sleep mode all day and was at about 95% when I plugged it in, but it charged the remaining few percent and powered my macbook for the 4 hour flight. I've heard that it doesn't really have the juice to recharge a battery and some have suggested removing it, but mine is internal so I couldn't. So maybe that system had more power? Or no one else was really using it? I didn't see anyone else in EC powering anything, but didn't bother to check further back.