I bought it, as a partial birthday present, for me. Though it had to be shipped.. came much sooner, even with free shipping (I went to the store for my others).Anyway, at first.. took a while to charge. It doesn't come with it's own charger. Then, I researched, and found that is needs at least 1 amp.to charge a bit faster (no, it doesn't come with it's own charger, but comes with the USB cord. Took a bit of patience, but, once fully, or even partially charged (it came with 28, so ..the fully charged thing is not true). I plugged it into 3 cell phones, (not at the same time), but.. It charged a 7.1 Android at 50%, a cheap battery vampire phone at 0%, and my friend's more expensive phone, at 15%, to 100% in less than an hour..and still had 75% power left. THAT in itself makes it a keeper: Charges most phones, faster than the chargers that come with the phones. Now.. if your phone comes with a less 800 to 1 amp charger.. use at your own risk. I don't think it is a risk.: You need to have spare power, in an emergency, so.. Also.. it seems durable (haven't dropped it, yet). It is a bit larger than some of the others (and as slippery). However.. put it into your pocket, or glove box. AND it also has the screen that lets you know how much energy that it has left IN or OUT. Sometimes that is important: (I am old, celebrated my birthday, and am sometimes tipsy, soo) when the cool battery blinks.. need to know: is it charging itself, or charging the phone that I just found
And it is a bit fool/curios proof: It ididn't say it, and I KNOW better: wonder if it can charge itself (there goes the warranty :-) ) It shuts down.
Did I mention that it has a flashlight?
And the on an off button may depend on your phone.. If you plug it into your computer, the light comes on (not the flashlight).
Personally, if they ever go on sale, again, I have a few friends that I would buy them as gifts for. If I had my own kids (have nieces, nephews, and other kids that I look out for). HOWEVER.. remember: charge it up.