This product - to date - works perfectly well.
I found a satisfactory autonomy, much higher than my original battery very tired after 2.5 years of loyal service.
The comparison is difficult between the two: my phone usage is different between now and there 2years.
I did as the instructions advocates: 100% load by 30% and then to charge by turning on the usual features (WiFi, 3G, application).
My battery gauge decreases normally.
Only remark: the battery autonomy time evaluation: it became dummy (which is not necessarily abnormal because battery is not the same brand)
So: the result, with normal use, I almost 48h Autonomous qqes telephone network and business applications.