I've had this unit for a couple of weeks now. Its main function for me is powering my iPhone 4S while I'm using a GPS app like MapMyRide which sucks the phone's internal battery to under 20% in 3-4 hours. It's heavy at 12 ounces but it packs a huge load of energy, 12,000 mAh, which, I think is 12 full Amp hours. Complete specs can be found at the mfr's site.
Part of my tests was to run my phone down to 30-40% and see how many full charges I could get out of the NewTrent. Answer: 9 before it stopped providing a charge output implying it could recharge an iPad mini or iPad retina from 50% to full maybe 3 times.
Pros: Bombproof case, water-resistant door protects the output connections, dual USB jacks for 1Amp and 2Amp outputs, recharges quickly from a 2A USB device and not so quickly from a 1A USB jack.
Cons: Heavy, door on the output jacks is a bit flimsy, no water protection when cables are plugged in, requires odd USB charging cable ("SD," hard to find but apparently it's all the rage for non-Apple phones so I wouldn't know), remaining charge indicator is difficult to see, truly bum-numbing gray color.
Would I recommend that you buy one? Not yet. Wait for more user reviews to show up around the webs. But if you need a high capacity power pack in your hands in a few days, I don't think you'll regret spending $60. There are dozens of similar devices on the market in varying capacities and with a variety of features and conveniences. Not many are water resistant and armored like this one.
I have not examined the physics carefully or run the numbers but I think it would take about 14 days of direct sunlight to top it off using my little Goal Zero #3.5 solar collector, if it was possible at all.