I know this is a touchy issue, but in my opinion it's Coffee Lab. They have a great coffee bar at the hospital in the North Shore, but now you can also go to the Café in Wairau Valley. It's a really cool place and you can see them roasting the beans on premiss on roasting day. They bring in fair trade coffee directly from the farms, then roast them in house. And a flat white is only 4$! I'm finding is rare to get a really good flat white in Auckland for 4$ anymore. You can also pick your roast, which is awesome if your a real coffee nerd. If you're not, the Baristas know what their doing and you can trust them to make you a good cup of coffee.
That's my humble opinion; where do you think the best coffee in Auckland is?
Also, here's their info: