USA Today has an interesting story this morning about the frustrating lack of power outlets in most coach cabins. Very few airplanes have power outlets on short-haul flights, and even on longer flights—when you're more likely to use your laptop to work or watch a movie—they are few and far between. American seems to have the most outlets, according to the article, but only every 2nd or 3rd row in coach. That makes it even more exasperating when your laptop gives out ten minutes into Glee, while the guy two rows up is happily plugged in, watching his Two and a Half Men reruns.
The worst: Discovering that for once you actually have a power port, but that you left the converter at home. You usually need some sort of converter, because most airline seats have cigarette lighter-style 75-watt plugs rather than regular two-prong AC outlets. (Here's the converter I use for my MacBook Pro. Important note: It doesn't actually charge the battery but provides power while you use it.)
Anyway, the good news is that airlines realize they have to add more power ports, since everyone these days travels with a laptop, iPhone, iPad, etc. What's more, in-flight Wi-Fi is becoming more and more common, and it can really drain your battery. Of course, if you upgrade to business class, you're golden: Most front-of-the-plane seats have a power source. But I always make sure my devices are fully charged before I take off, and pack a converter in case I get lucky.
P.S. You should check Seatguru.com to see if your assigned seat has a power port. I always check it when choosing a seat anyway, in case I'm inadvertently putting myself in a spot that doesn't recline or has limited legroom.