Back in the 80's, when my sons were just kids, we went Melbourne to Brisbane, with the car, via the Southern Aurora and Gold Coast Motorail. It was a great trip, and the boys loved it. I can still recall it quite vividly.
Its very interesting really, while the GCMR took longer than the XPT, it had a better overall service, with the dining car, not just a floating pie shop as it is now with the luxury of frozen meals heated in the micro wave. And the old pie now costs around 50.c short of $7.00 as the meal options in a come and get it announcement.
The Motor rail service also was usually around 70% full in off peak and in holiday times two car carriers were on the train, a good wash was included in the price, helped with diesel dust and any other road grime though. I don't know the numbers in the sleepers but on each occasion I was on board or picked my family up, the numbers seemed good and the sitting cars also were more often than not well patronised.
While it was more a long distance tourist train, it used to have locals from Casino, Lismore and other stations travel to Byron Bay for a day at the beach, in summer was older people, in winter it was the wet suit boardies. Still it provided income for State Rail, as they travelled to the Bay and back on the same train.
The replacement with the XPT I found drove people away from using the service. Didn't help when the privatisation of the freight side of services came in for the branch and with the loss of all the freight to each location, well not really loss, but turned away, only the X marked the spots. The rest is history.