Summary: I was taking a long plane trip, and would not have the chance to charge up my iPod in between legs. This seemed like a great option, as the alternatives had AA batteries. [I had one of those Belkin iPod battery packs, and it was awful!]

It has a removable AC plug, which clips into the underside of the battery pack. This allows the battery pack to remain sleek when in use. I assume they have different AC plugs, depending upon the country you buy the unit in. It would be nice had they included other plugs, so when you go travelling internationally, you could plug it in directly. I had to use an adapter plug to convert the US plug to a European plug. Just don't lose it, or you'll be out of luck! But if you do (!!), you can also charge the unit with the included USB cable via a computer's USB port. This is similar to how the iPod can be charged.

Okay, enough background. How does it work? Wonderfully! I went on a 10-hour flight over to Europe, and never ran out of juice. And that says alot, because I was watching video, and using the iPod's screen alot. It worked the same for the return trip, though I did charge it before heading home.

You can also use it to charge up a cell phone or blackberry, as long as they have a USB plub as a charger. I'm not sure whether APC offers different cables.

Overally, I am extremely satisfied. My only knock is that the pack is quite expensive.

Summary: I find the Universal Battery(Lithium Polymer 10Wh) very versatile. I've used it to recharge my cell phone/PDA completely during a 2 hour flight. It still had plenty of power left for my iPod.