I think the program is bad value for Australian flyers. The value of Eltie is mostly in the upgrades. I am currently flying BP on all of my flights I've booked because of APD and guaranteed upgrades.
But if you lived in Australia? Ugh. To fly anywhere you'd have to go through Auckland. It would be much nicer to just fly direct.
It really does feel like a New Zealand specific program, not because of the benefits persay being New Zealand focused, but simply because Air NZ does all its international flights out of Auckland.