Observations of some 45 years of international flying (including a lot of Quantas).
Quantas Downside: 1971. 1st class seat. Singapore/Heathrow. On unpacking at home found that items had been stolen from baggage. Made report to Quantas London & was essentially told "tough titty - you should have lodged a report at the airport." End result - The big Roo was black-listed for all company and vacation travel for self and employees for 4 years and Quantas couldn't be bothered even acknowledging their banishment.
Quantas Upside: 1980. steerage fares. Sydney/Toronto. Ex wife not allowed to board at Sydney due to not having an American transit visa (refuelling stop @ Honolulu) Quantas Mascot staff provided hotel accomodation and facilitated telexed issue of the necessary visa within 12 hours even though the balls-up belonged to the booking agent.
Most horrid flight : Air India 1977. New Delhi/ Kuwait. Middle of the night landing in Aden so hard that all the oxy masks deployed and the aircraft shut down on the runway at the end of the roll. Two hours sitting in the dark with no information, no APU, and therefore, no lights or airconditioning. Worst part of all - no alternative!
Most enjoyable flight: TEAL (pre-decessor of Air NZ) 1966. economy. Fiji/Auckland. There were more cabin staff than there were passengers and they killed us with kindness and, joy of joys - I was a bachelor!
All that said, over the past twenty-odd years when it seems that everybody and their damn dog is flying, on international sectors I've generally found that if the check-in staff are reasonably efficient and the cabin staff keep the masses under control, one carrier is pretty much the same as the next. In short, bad handling of a passenger in any aspect on one sector can poison a carrier's reputation for the rest of time no matter what rabbits they can subsequently pull out of the hat. In almost all facets tho, despite some of their marketing practices, IMHO I reckon we have it pretty good with our National airline. (but then, maybe I spent too much time in the 3rd world jungles??) Best way to avoid airport/airline hassles is "STAY HOME" & fly your own for fun. Cheers Riley