I've used this for a while now and tried it with iPhone 4s and 5 and some Droid phones and it works great.  It can charge a phone 3-4 times with battery to spare.  Easy to recharge, just plug in the USB cable.  While it can charge an iPad it cna't charge it fully.  If you need extra power for smartphones or other small devices this is great.  If your looking for tablet power look for a larger capacity external battery.