If you are going to stay at the YHA in Auckland (I guess the YHA is not the best option there, I just stayed because the better hostels were fully booked) stay at the International, not the City one. I stayed at both and would definitely recommend this one.
I spent NYE there and found it adequate. There are good common facilities (kitchen, toilets, showers) and reasonably clean. The atmosphere is not too bad and you have some space to get to know people if that's what you want. If not, it is still okay - the place didn't seem like a teenage party hostel.
It is not too far from the city centre and there is a free bus that take you to the nearest supermarket. The bedrooms are not too bad but my mattress was very thin and the noise from the street was loud. An average hostel but okay for a night.
