I have this battery for less than a month, and already two of my colleagues have ordered exactly. Bored by cheap batteries that drop after qqs months without ever really charge the iphone? You have found your happiness. I think even buy a smaller when conditions are less energy (as a journalist 3G is paramount and it is not unusual to find 15% energy after qqs hours).
Only drawback, it seems that the supplied cable may fail to supply the iphone with the adapter. Loose connection? No big deal, I pass me that little bit and use a dedicated cable to the load.