Melbourne is beautiful. We have been here several times now. On this cruise we just got the tram into the city and boarded the free, hop on hop off tourist bus which stops at many places of interest through the city.
I loved Dunedin. We took a ship organised tour to Lanarch Castle which was worth a look and was a nice drive out of the city. Then we just wandered through the city centre. There arn't a lot of shops if thats your thing.
The port of Auckland is very close to the actual city centre and it is not particularly pretty, Auckland was quite nice though. We booked a hop on hop off bus and visited Kelly Tarltons Antarctic world and the sky tower with both being well worth a look