The Fire only packs a 2,400mAh battery, which is small compared with the competition. Battery life is average and will last a full day... as long as you don't activate Dynamic Perspective and Firefly. (You know, the phone's two most unique features.) These two things are such a huge drain on the device's battery that I had to charge it up twice in the same day -- once in the early afternoon and again later that night. It wasn't uncommon to lose 10 percent of my charge in a half-hour. So if you plan on using Firefly for comparison shopping, make sure you shop for an external charger first. In my endless-video loop test, meanwhile, the phone lasted nearly nine hours before dying. This is about average for a battery of this size, but then again, Amazon's fancy features weren't running at the time. The audio quality is better than most. Calls were clear; in-call volume was more than adequate; and the stereo speakers were loud, if a little tinny. The phone's GPS also performed admirably, helping me navigate multiple routes without any lost connections.
Sources: The Verge, Gizmodo, Engadget, The New York Times