@bramzee, mileage can vary wildly between phones, even examples of the same model. This is because the phone is the device powering the ring and if that power transfer isn't properly efficient then you get poor communication, tiny sweet spots etc. A properly built and well maintained phone has a far better hit rate with the NFC Ring (I've had great success with the Xperia range, they have an excellent antenna size and design).
It does look like phone manufacturers will be adjusting the way they do things though and this should mean a major improvement from the active reader side of things in the future.
C