I can see how this is fantastic for people who are on the go, away from their desk, or in meetings all day, work outdoors, fly a lot, or use public transportation as opposed to a car where you could use a car charger. I use my iPhone so much I am often out of battery as early as 11am and know how frustrating this is.
However, I just could not bring myself to putting a device on my iPhone that completely destroys the device's aesthetic appeal and beautifully designed lines. If they had managed to keep the iPhone's exterior flush by either completely covering the bottom side, or the backside, or both -- keeping the straight lines and just adding some millimeters length or depth it would be acceptable to me. Instead, the device makes the iPhone look like a monolithic remnant from the 80's. It's just not working.