Well, the green light on my adapter wasn't on, so it wasn't receiving any power (it will come on even in a a car with a really low battery--it'll just start pulsing on and off when you then plug it into the laptop).

I might look into an iGO product, but I was mostly just excited to try it out for the first time (especially after advocating in the AS forum that AS should install power ports to go along with their on-board wireless Internet). I've got another set of DL flights in a couple weeks--will have to see if there are any EmPower-equipped aircraft and try it again...thanks for the help!