This sounds like a fantastic deal for two first class tickets -- although I guess if you take the islands stopover it will be in biz... is it the cheapest ever?

One slight concern that would stop me from booking is this line from the terms and conditions:

"Round trip airfare per person on specified Air New Zealand flights in Economy Class"

.. which may or not be a mistake.

The other interesting thing about the current crop of specials on the airnz.co.uk site is that rather than the cheap deals all being non-mileage earning the destination CHC deal is fully (disc econ?) earning, while the AKL earns points/km only for the transatlantic sectors.