I recently got them to release a J seat in December on BNE-HKG during the busier travel season, so it's definitely doable. Obviously you'll have to pay the award assistance fee.
I think the rates are pretty good. Here is a purchase with the Visa debit card.
Credit Card Charges Results
Date on transaction receipt:
December 20, 2011
Amount on transaction receipt:
264.00 NZD
Mid-market rate for NZD to AUD on 2011.12.20:
(Excluding bank charges)
0.764321...