I think its a step in the right direction. Why should NZ take the risk of having people here who travelled on forged documents if there is technology to prevent it?
A well forged passport is worth tens of thousands of dollars..... you dont spend that kind of $$$ unless you have something serious to hide. Its very airy fairy to suggest that its an invasion of privacy and in turn we should just let everyone in.
Idealy iris scans will eventually replace the need to travel on a passport at all.