I live in auckland, and I always read about burglars in my area (St. Heliers) but my house is still safe.
As in any city in the world, if you stay away from downtown at night or from the 'bad' neighborhoods it's ok.
But yeah, maori gangs are a problem and those can be some really scare guys.
I was sitting the other day on a beach side cafe about 3 blocks from my house, and this car with a bunch of maoris kept driving by yelling and insulting at all the people. And of course, not a police car around, ever.
I feel safer than say, Mexico City , where I lived for a year, but it's not really paradise.