From Engadget on battery:
We already know better than to expect the Vita to pack enough juice to get us through an international (or even domestic) flight, but we couldn't resist running it through a handful of battery tests anyway. Our first few power drains matched our review of the Japanese unit almost exactly -- three hours of dedicated gaming on the console's default settings left our handheld dead. Dragging the Vita's brightness slider down to its dimmest setting scored us another hour of playtime, and kicking the console into flight mode seemed to buy it another twenty minutes. We were able to game for a little longer in PSP mode, stretching the battery to nearly six hours of gameplay on the minimum brightness level with WiFi and audio disabled. We were hoping to drag the handheld's longevity out a bit further than this, but were unable to get the Vita off of the company line -- our game-heavy battery tests match the Vita's official battery life estimates almost blow-for-blow. Three to five hours of gameplay -- it's what Sony promised, and it's what we got.
Sony seems to have made looser estimates for media playback, however. Although audio playback fell just a few minutes shy of the rated nine hours, our video test eclipsed the expected five-hour runtime by a full hour. Although the Vita's six hours of video playback isn't enough to make up for its other electrical shortcomings, we have to respect a device that can handle Gone with the Wind, complete with overture and intermissions, and still have enough juice left over for some light gaming. That's an inflight experience we could get behind. Despite our love of Rhett Butler, though, we still feel a bit let down by the Vita's longevity.