The reason why I chose this battery over others was because of the large charging capacity especially as I plan to use it outdoors. Also I wanted something that wouldn't be tied to one device or one iteration of iPhone. Let me start by saying I have only had the battery pack for a few days, but I can confirm that it does fully charge an iphone 3GS from 2% to full with plenty of power to spare at the same rate as a wall charger. I will update this review as the months pass by. PLEASE NOTE that this is the latest iteration of this product, at the time of writing this review the older version was still being sold on amazon.
Packaging looks great. You get USB wall charger with twin USB ports to charge the actual battery which also has a USB port. Using twin ports charges it faster according to the manual. You can also use twin USB ports on your computer to charge it. They bundle 3 leads in addition to the main charging lead, one for apple devices, one for blackberry and one for HTC (which is a mini USB anyway) so I suppose in theory you can use the battery to charge almost anything as long as the power lead has a standard USB connection on one end. The three LED lights show you roughly how much power the battery has and there is also a small LED torch should you need it. Size is thicker but smaller than an iphone. They also include a small soft carry pouch.
Thoroughly recommended.