I want to. An old family friend from Connecticut originally, got a job down at <a href="http://www.otago.ac.nz">University of Otago</a> in Dunedin and seemed to really like it. It seeems to have a much milder climate than Oz. He and his wife had to move, and are now in Seattle, which apparently resembles NZ climatewise.
I spent some time on the north island some years back, for a couple of days and nights, and I found it strikingly beautiful. Rolling hills for all around, and just so much natural beauty. The nightlife in Auckland and Wellington is pretty decent, too. Highly recommended -- and one of these days, my wife and I will have to go back there for an extended visit. If I had to choose between Auckland and Wellington for the whole package, go to Wellington. That also puts you in close proximity to the south island, too.
You can spend a week doing each island. I've only been around the South Island- twice, and you must go to Christchurch, Dunedin, Te-Anau, Milford, Mt Cook, Queenstown, Fox & Franz Josef and back through the mountains. If you want to party, just stick to Queenstown, if you want to see beautiful scenery, then go to the places I've mentioned above! Gets cold during winter- read snow- so I'd recommend anytime in between Nov to March to go, unless you want to fit in some skiiing as well.
I went for two weeks several years ago. Loved it, I'd go back in a heartbeat. I spent about a week on each island but it didn't feel like nearly enough time to fully explore the place (the country is about the size of California.)