We had a group of 40 seniors from Florida who stayed 3 days in Auckland and then took the Diamond Princess to Sydney. The ship is very clean and comfortable. I would rate the food as the best I have had in 10 cruises on different lines. The ports were decent - Tauranga, Christchurch, Dunedin, Hobart, Melborne. Be aware that these ports are very much like being in the US as most AU/NZ cities have the look and feel of American cities.
My only complaints on the ship were the VERY small theater and limited gym. Since we were usually some of the last done with early seating dinner, 3 nights we could not get a seat for the 8:15 show when we got there at 7:55. That was a disappointment. Also, if you want a tradmill, you will have to wait in line nearly any time of day. They did have more free fitness classes than most lines, but sorely limited equipment.
The staff was wonderful....particularly food service. Lots to do on sea days.We had 30-foot waves on our crossing to Tasmania, but the captain kept us informed and the crew was very helpful.