I also ordered this charger some time ago (looks nearly identical to the original one).
With Nexus 4 I had no success charging.
First the phone always slips down after some minutes. When fixing it a bit, green light of charger was ok, phone also recognizes the charger with a sound. It also displays "charging" but does not really do so. So if placed for some hour, there was still the same percentage or less in the phone display.
On the other side, I gave the charger to a friend who owns a Nexus 7 , and he says that the tablet was fully charged.