mattwnz: Is hop card the same thing as snapper, which we have down here in wellington? I have never had any problem with these systems, and they have been operating down here for many years.
I've had a number of charging issues with snapper, however you have to go to one of the few snapper service centres or have a feeder to get any refunds back on your card.
Going slightly O/T - The AT / Snapper Hop situation is a bit of a screw up. The Thalas system is meant to be suitable for nationwide implementation which NZTA should be looking after but I've yet to see any other regions outside of Auckland so far.
Hopefully it will reach Wellington and integrated ticketing will be rolled out. I think that the Greater Wellington regional council is awaiting for the Auckland system to be bedded in - Integrated fares are coming shortly so maybe us Wellingtonians will not have to carry multiple cards and cash in the near future.