Maybe we should run our own little test on the effectiveness of the Q tags over printed tags. If you're travelling with two bags, apply the Q tag to one and put a thermal printed tag on the other (without adding any of the 'Business' or 'Priority' tags). Then at the other end, wait at the carousel and count.
Bit hard to do that (not apply priority or business tags) because domesticity Qantas now prints the priority on the tags themselves.
My most recent experiance was SYD-CBR on QF787 2 weeks ago in J. Maybe 50 people waiting for bags. I Used Q tags my bags and both my bags were in the first 20 or so bags out so not too bad. Much better than the night before arriving on MH from KUL, one bag was one of the very first out, my second bag almost dead last.