Qride is "competency" based, and in my experience, if you are competent in the way you maneuver and control the bike, you'll get the certificate to get your license in one full day, but if you are awkward or it is evident you really could use additional practice, more than one day will be required.
If you have the opportunity to practice the tested skills (figure 8, emergency stop, etc) in advance that will probably help you to radiate competence during the Qride testing sessions. The skills and attitudes you'll cover in the class (defensive driving, emergency turning maneuvers & counter-steering, etc) are truly extremely valuable skills. I'd suggest approaching the class with an open mind, and trying to learn as much as you can.... after all you will be paying for it (to the tune of $300-350 for the one day) either way, instead of bringing a "this is a waste of my time and money" attitude into it, why not try to make it as enriching an experience as possible, and to get as much as you can out of it for your hard earned money?
Riding to the Q-ride training while unlicensed on the vehicle you are seeking to get a license for would strike me as... unnecessarily cocky, and not setting the right tone for the training, but that may just be me.
Q-ride is not the only option avaible, i'm pretty sure you can still test in the "traditional" way, by scheduling a road test with Queensland Transport, ...and that would be cheaper
If you have specific serious questions about the Qride experience, I can try to help... I've been through it once (about 1.5 yrs ago) on a scooter to get my RA license, and I am doing it again this next weekend on a motorcycle to get the A removed from my RA license, to get to my "R"'s.