Just briefly, have flown NZ Premium Econ a couple of times and I think it is overrated. I disagree with a previous poster about seat width. VS and Eva, to name just two airlines, offer wider seats in premium econ (for example, in the 747 VS layout in upper deck is 2-2 versus 2-3 for Air NZ. I also don't care about food and drink, and as a Star Gold can check in premium anyway. Having two crawl over two other passengers to reach the aisle in premium economy is a pain!
My overall impression is they have done this on the cheap, and missed a chance to create a really good product. You are better off in my view on United in the Economy Plus (which is free for premium passengers) or the old Thai planes, which have just as much or even more legroom in normal economy.
The only good thing in my view about the Air NZ premium econ is that you can try to use the standby 400 airpoints upgrade to get a business first bed.