For member Montecristo:
Sometimes, they hold the QF T3 to T1 bus, till its chockers standing room plus sitting down pax and then the bus will go off on its way from gate 15 via the internal road, to T1 and then have to get up the long escalator to int dep processing at T1, bypassing the T1 check in counters.
The good thing about the QF T3 to T1 system, is that if you have your BP issued at another Aus dom airport, from QF, you can bypass the checkin counter at T1, and just go through to int sec screening, and outgoing smartgate.
VA no longer does this bus service like it used to, as what QF still has, so, if you have to fly out of Aus, and live in ADL/HBA or another airport (better to fly out of Aus with QF), that does not have QFi flights, going out via SYD is ok, tho, going out through MEL is better, as the terminals are all linked, ie walkable.
Going out through MEL is also good now, if you have to overnight there, as there is a new Ibis and Novotel Hotel, out near the AFP/ABF building, on the other side of the multistorey carpark.
SYD Novotel Airport, is far away from T1.