Despite the fact New Zealand have given the game the R18 rating, the country will be receiving the same censored version of the game it's neighbour Australia is getting. The R18 rating means it's illegal for New Zealanders under the age of 18 to buy the game, so why they're getting a censored version is unknown. No previous GTA games were edited for New Zealand, only Australians have suffered that, due to the fact the current highest rating there is MA15+.
Rockstar still haven't confirmed what exactly has been cut, though they assure us it's nothing that will compromise gameplay. For any Aussies or New Zealanders wanting an uncut version of the game, your best bet is probably importing from the UK (if you require a PAL version).