I used Ultimate Juice for a while. In my opinion it is only good for someone who leaves their phone off for a long period of time. If you are constantly answering texts and emails and such, I don't think it would be very good. With this app, the 3G gets turned off once the screen goes off and turns on when you turn the screen on. If you are constantly turning the screen on and off, I don't think it is very good to be turning the 3G on and off so frequently. Not sure if this would damage anything but it just doesn't seem good for the phone. I did not see very much increase in battery life either when I was using it either. But it's worth giving it a shot if you want if you keep your phone off for long periods of time.