My wife and I recently returned from a 4 week (non-biking) trip to New Zealand. We spent 1 week on the North Island and 3 weeks in the South. It is unbelievably pretty with so many varied things to see is such a small place. I highly recommend a trip there, either on or off a bike.
I've written an article about some things that people looking to tour there might like to know in advance. There are 14 observations broken into two sections: Highways and General Bicycle Touring.
Here are all 14:
Cars in New Zealand have the right of way.
There are no shoulders on New Zealand highways.
New Zealand has only 2 lane roads
Drunk driving seems to be a serious problem in New Zealand
There are very few stops signs in New Zealand
There are many one-lane bridges in New Zealand
New Zealand was expensive
Subway sandwich shops in most larger towns
There are long distances between places of resupply in New Zealand's South Island
Organic food is not readily available in New Zealand
Bicycle shops seemed plentiful
Public rest rooms in New Zealand are widely available and clean
The wind can be very strong in New Zealand
The roads in New Zealand can be very steep