We travelled from Melbourne to Singapore and back with our 6 months old.
I would not recommend Qantas for travelling with an infant. First of all, even though they charged us 10% of adult fare for our DS, they would not guarantee a bassinet for us. We had to actually check in at the airport before it was booked. They just told us to get there 3 hours before the flight. I even called them on the morning to see if they could tell us if there were sufficient bassinets for everyone that requested them and they refused to let me know. They just told me again that we should get to the airport at least 3 hours early to check in early and try to secure a bassinet.
On the way to Singapore we got pre-boarding, to board with business class but on the way back we did not. We had to just board with general boarding.
The change tables on board are very unsafe - just a sideways little pull-down table with no raised edge or belt to secure DS while changing him. I had to try and lean forward and push my body against the edge of the table to stop him rolling or bouncing off.
The bassinets are next to the catering trolley storage so the whole trip the flight attendants were slamming the trolleys into and out of the storage cupboards and slamming the cupboard doors right against the wall that held the bassinet.
On the way back we were not offered an infant belt, so we had to ask for one just before take-off.
There was no assistance or help from flight attendants any time during the trip. The only "kindly" behaviour was that they would stop and talk to DS while he was in the bassinet trying to settle himself. This would of course make him cry as soon as they walked away. Perhaps none of them have had a baby themselves before (and know that you don't get them all excited when they are trying to sleep).
All in all a BAD experience. I don't know if any of these things are standard across airlines because this is the first time I have travelled with an infant... I hope others are better.