I've been to NZ in the last 10 years(2015), and used Here maps (because I was able to download the entire country map and use them all offline) and had no problem there. I was in the south part of the South Island, from Dunedin in through Roxborough and Alexandra, so not the case of just sticking to Auckland or anything.
Disclaimer: I'm from New Zealand. Map data is constantly out of date here, no matter which vendor you deal with. Google, Apple, Bing, OSM, whatever. For me, double checking is no problem.