Having complained about iPhone 3G battery life in the past, I was thrilled when I received a 3G Juice battery for the iPhone 3G. The device came in a nice black box that fits with the whole "I am an iPhone accessory and need to look cool" mantra of today's Apple compatible devices.
When you open the box, you get a slick looking glossy black battery which is about half the size of an iPhone with similar thickness and appearance.
To test, I let the iPhone 3G battery drain completely and plugged in the 3G Juice device and voila, it was fully charged in short order. In my tests the iPhone charged approximately one percent a minute meaning the iPhone gets fully charged in under two hours.
I let the iPhone drain completely again and plugged in the 3G Juice battery one more time and received about a 20% charge.
To charge the 3G Juice battery you use the enclosed mini-USB adapter which allows you to use any USB port to power the battery.
It is hard to suggest room for improvement - the battery has an on/off switch and an LED to tell you when the battery is fully charged and powering the iPhone. There isn't much to wish for really.
The Amazon price is $50 and when I ordered this battery about a month ago, I also ordered a similar one from Kensington. Interestingly, about a week ago, Amazon informed me the Kensington device is out of stock and cancelled my order.
So for now, I can say I am highly satisfied with the 3G Juice battery and when I have it with me, I no longer have to conserve my use of my iPhone.