UPDATED: Since I wrote this, two things have changed. First, Air NZ has since announced that it is RETAINING Airpoints Upgrades of fixed value for its Gold Elites. However, it appears that they will only be confirmed on checkin, when previously they could be confirmed up to one-year in advance. It appears they will come AFTER OneUp upgrade bids, which means Gold Elites don't exactly get priority, but rather the crumbs.
Secondly, Air NZ's communications to its status Airpoints members have indicated that their OneUp upgrade bids will actually be higher value than those without status. Silver Airpoints members will have a "premium value" layered on top of their bids, but it is unclear what this means (1%, 10%?). Gold Airpoints members will have a premium value of "three times that of Silver", but again what does that mean? Gold Elite is more again.
My chief concern about all of this is the lack of transparency. I have never minded throwing in an airpoints upgrade request and taking my chances, knowing full well that my chances depend, in part, on my status. Gold Elite's first, Golds second, Silvers third, everyone else below that. However, to engage in an auction, where anyone can bid, with cash, not knowing what status means, just cheapens the experience.
I am happy for Air NZ to introduce OneUp upgrades. Sure, feel free to flog off upgrades to anyone, if you have any left after those with status. However, give your status Airpoints holders first preference. Make the leap from economy to business premier much more expensive in Airpoints dollars terms than it is now (because that doesn't reflect the fare difference), but make sure status holders feel valued.