I received some feedback direct from QF recently, but wanted to wait until I had tested it out to confirm. medhead, I think you'll be particularly interested in this news.
They have (partially) fixed the problem with the remaining-value re-issued vouchers, which previously wouldn't let you manage the booking with MMB after you'd redeemed it, and you'd have to ring up and get some additional comments removed to allow MMB to function as normal.
Well, apparently, they've implemented a script which runs at a certain time of day to remove these comments on bookings made with these vouchers, which then allows you to use MMB.
I tested this yesterday, and as soon as I tried to use MMB for a booking (booked at 12pm), it failed as usual (even after the ticket was issued). When I went back about 10pm (QLD time), I could manage the booking. I think I remember my contact saying that the script runs daily on weekdays...?