This product is great for what I was looking for; a small power source that I can leave in my backpack or through into my girlfriends purse.  I have been using this battery pack for a few weeks now and the device does not seem to lose power when idle.  On average I can charge my iphone 4S FOUR times (usually at around 20% battery life).  They advertise this to charge mostly cell phones, but it can basically charge anything with a USB attachment.  I have charge my Nike Fuel Band, Plantronics bluetooth headset, Logitech Harmony Remote, USB Fan, and Ipad keyboard/cover.  All around this thing does a great job.  I also own another New Trent power pack, but it holds twice the power but is nearly twice the size...  So if your looking for something that will last you the weekend, and are using your devices with regular use, this is probably what you want.  Now if you want more power and are willing to lug around something larger, get a hire capacity power pack.