Prickly Fern

You need a car in New Zealand to get around unless you live and work within walking distance.
Relying on buses and trains on a daily basis will disappoint you. Public transportation is simply a joke at best. However, driving around New Zealand isn't the best either.

I read once on Statistics New Zealand site or somewhere that New Zealand has one of the highest rate of car ownership per capita in the world. (looking for this number I stumbled upon this article, which is quite a good read about the kiwi car craze)
Looking at the population of New Zealand you would not think traffic would be one of the worries.
But it is.
Auckland, like other big cities in New Zealand, was not designed to handle large number of cars.
Roads are simply not enough for the peak times. For instance there's only one bridge, The Harbour Bridge (which is small anyway) that connects one of the major parts of the city to the central. And when people look at using public transport as the last resort and keep driving, the problem gets bigger by the day.

They are trying to rectify the problem by building bypasses and bus lanes and things like that but the core remains clogged. I can't see it getting fixed.

Attitude of New Zealand drivers differ from most of the western world (maybe not Italians). They are very aggressive drivers. The competitive nature of kiwis show itself very bluntly on the roads. Generally people obey the rules and follow the signs, but when there's instincts to follow then they just go. Pedestrians pretty much have no rights -including the sidewalks/pathways- unless there's a crosswalk with clear signs. You have to be very careful -especially in Auckland- walking on the sidewalks and crossing corners. Chances are nobody will stop and give way to you even if you are pushing a baby in a stroller. And I mean this because numerous times I have been almost ran over by cars turning fast corners into side streets, and pulling out of blind driveways at 50km/h.
It is very advisable to cross streets only at traffic lights or crosswalks.

This is going to sound like I am a fussy bugger but traffic lights in New Zealand seem to take a very very long time to change. Logic to the lights' changing order remains a mystery to me amongst other traffic rules (like giving way to upcoming traffic if you're turning left or not being able to turn left on red to straight traffic). Most places don't have the night setting or non peak setting for the lights. It's one big waiting game all the time. If this is different somewhere else in New Zealand please inform us.

If you're driving around trying to find your destination in New Zealand you need to be very patient. Don't leave home without a CURRENT map as there could be a street in your way that was built after your map was printed.
Don't assume the road you've been driving on will have the same name until it runs out. No, the road names, street names will change without any notice or signs even though it is the same stretch of asphalt. God forbid there's a slight curve on the road's layout, its name needs changing!
You'll be lucky to find the street name sign posted more than twice -one at the start one at the end. (OK maybe few more times on big ones)
Until you get to know your roads, driving in New Zealand requires expert navigational skills and a fast reflex. By fast reflex I mean an ability to respond to sudden changes in your position in traffic.
You may be driving on your lane, cross the street at the intersection, and all of a sudden you are facing upcoming traffic. You may be driving on a lane with straight arrows, and 10 meters to the light you find yourself restricted to right turning only. You may be doing a casual inner city cruise-around only to end up on a highway that takes you away.
Bottom line: Don't expect every lane distribution change to be clearly signed in advance.

Long distance driving could make you sick. Be prepared for winding roads. Also watch out for one lane bridges. Most of the main highways run through rural lands and they are basically one lane each way. But sometimes you have to go through these one lane bridges and one side has to give way to the upcoming traffic. The scariest one I know is at Mt Messenger going to Taranaki. It's actually a one lane tunnel!

Cycling for daily commuting is advisable only if you are into extreme sports. Auckland does not have dedicated bike lanes in the city because there's hardly any room for cars anyway. There are some around the suburbs but they are meant to be for recreational purposes, not to be taken as means for a serious mode of transport. It is pretty strange because there are a lot of cyclists in New Zealand who choose to drive to work.
If you are keen enough to cycle to work everyday, you need to be extremely watchful of cars passing you and cutting you off. Bus drivers are notorious for giving cyclists hard times.
There's a few deaths every year caused by cycling accidents.

In summary, don't come to New Zealand thinking you will have cruisy times on the roads. :)