I just returned from a trip to Australia using OnePass miles for 2 F seats on QF. I had no trouble securing 2 F seats, but you have to be reasonable and flexible. For example, I called about 9 months ahead of the window I wanted to travel during, I was flexible on specific dates and days of the week, and I was willing to fly into one city and return from another in OZ (e.g., into Sydney and out of Melbourne). My only criteria: I wanted 14 days in Australia. OnePass partner desk took a few days and then called me with an itinerary.

P.S. F is definitely worth the extra miles! It was the best international service I've ever had - and even contrary to popular opinion, was even better than a flight in SQ F I had a couple of years ago. Have fun in OZ!