This battery is great for those long trips away from the home. I use it particularly for ingress which sucks all life out of my nexus 4 at the moment. The power pack solves my problem! You can charge a couple of friends or devices at the same time too which adds to it's usefulness. Well worth getting.
This will not work with a Nexus 4 or other Qi compatible devices. It didn't follow the standard wireless charging protocols, so future devices will also not charge on it. Waste of money even if reduced further.