I was unhappy early on with the battery life on my D3 so I got Juice defender Pro. I set it on balanced and forgot about it. It totally made my Droid laggy and sleepy. It was always waking up from having it's wifi or 3G data services turned off. I had to wait for FB and other apps all the time. I was beginning to think that the phone was crap. I turned Juice Defender off the other day and the device is alive again. I'm sure I can tweek JD and turn it on again but the battery life isn't noticeably different.