I bought this to keep my iPhone 3Gs charged on a five-day rock climb where we would have cell coverage the whole time but no plug ins (obviously). At the end of the first day, my iPhone battery power was very low. They are notorious for using power quickly, and it had gone down to less than 10%. The iGo gave me only a few extra minutes of charge. I left it connected overnight, hoping for the best. In the morning I found that it had shut off. After another attempt, I concluded that it was broken. No phone for the rest of the trip.Back home, I tried it again. With the iPhone at about a 50% charge, the iGo seemed to work as described and topped up the battery. Conclusion--Don't let your iPhone power get too low, because it won't bring you back from the brink. I would also have preferred that instead of the rigid "tip" design, there be a short flexible wire connection so the arrangement doesn't have to be kept in a straight line when charging. And yes, the blue light "on" indicator is annoyingly bright.