The Good

NZ is everything you ever dreamed about or have seen in the movies. As a tourist destination the exchange is mostly favorable and the landscape awesome. Make sure you figure out what your focus while here will be and try to stick your itinerary the first time. Places to go that may differ from your tourism list: Certainly go to Rotorua, but don’t miss the grandeur of Taupo, Certainly visit Queenstown (quite expensive) but don’t miss Christchurch or Kaikoura. Many people believe the South Island has better scenery than the North Island. Only 1/3rd of the population lives in the South Island.

Maori Culture
Excellent point of difference. Try to take in an official Hangi (feast with dancing), stay with the tours where possible and be sure to ask around about who is the best. In Rotorua alone there are many but only a few are excellent. 

Landscape
One of the key features of New Zealand is the scenery and native wildlife (birds and small animals - nothing that will eat you). Be sure to venture out a bit and spend a few hours on one of the many tracks around NZ. 

The Bad

Driving: As you know NZ subscribes to the left hand driving style still common in much of the former British Empire and Japan . If you have never done this before, make sure you are rested and alert so you have the time to get acclimatized. Unskilled Visitor drivers are one of the great dangers in NZ as all your instincts are out of whack if you are driving on the left for the first time.

Road Rules: NZ has a few different road rules so if you drive you had better learn them beforehand. 

Drivers: NZ drivers are rated low down on the best drivers of the world lists. While many are quite good, the good a tarred by the actions of the many idiots that have grown up with nominal driving code enforcement. In particular, watch out for turns into the opposite lane, these can ruin your day but are quite common here as are yellow light sprinters. 

The Ugly

New Zealand is a pretty safe place to travel around and is one of the most corrupt free places on earth however do take precautions with your personal items and always keep your passport and funds on your person.  Always lock car doors and never leave things in plain site.

Just plain Weird

NZ’rs rarely use the letter “E” so be careful of casual conversation. For example they typically replace the E. Example:  Bed is Bid, Head is hid.

You don't take a car to a "Body Shop" as this has a whole new conotoation in NZ - you take it to a "panelbeater".

Other good Ideas

On your trip to NZ one of the best stop-offs is Atutaki in the Cook Islands , Raratonga: Fabulous Pacific Island fair using the NZ$ and generally speaking English. And if you use Air New Zealand, quite often the stop there is free.