I experienced this only last week. I was on the 6am from Adelaide to Syd for the QF23 to Bangkok at 9.50. I was wondering at the time I booked how short the connection time was - would have much rather been a later flight. Lucky there was no fog etc in the morning but when got to Syd - I had never seen such a long queue to the bus! Then started stressing, but then they called those on my flight to come forward. Just missed that bus, on next ok but then it waited at least 10 mins or more for other buses I guess before we could even get off. Then of course the immigration queues. After much stressing I did make the gate, although I think it ended up being delayed anyway so that did help a bit.
But the other thing which is annoying (coming from Adelaide), last year I went to Hawaii and the return flight does not arrive in time to catch a connecting flight - so have the extra expense and inconvenience of paying for a night in Sydney. I dont see why it could not leave an hour or 2 earlier in day.