Flew QF532 SYD-BNE today with my online checkin. My partner and I got to the gate at T3 to use our new online boarding passes - to be told to go to the desk and replace it with a boarding pass because it is only a booking confirmation. When I insisted that it actually is a boarding pass, and that the "barcode" can be scanned, the flight attendant had no idea how to do it - having read this site, I showed him - lie the barcode down on the scanner and hold it still over the site where the barcode signifier is - and lo and behold, I was checked in! The flight attendant was shocked - they reported they had been told nothing about this, and he thanked me for being able to educate him. He even made a point of coming down to me in economy and offering me an extra meal as a thank you!
QANTAS may have launched online checkin, but they HAVE NOT adequately briefed their staff, which is surprising, since everyone is using it now!
I can see problems with it though, because it's possible to print a boarding pass with a given seat and then switch it by going through online checkin again, but you could potentially get into the airline cabin with the old boarding pass and then have a conflict with someone that been allotted your old seat. I expect there will be a few arguments over time over this!