If on QF1 (or any flight with a transit), you can also request that if the upgrade does not go through for the first leg, that you can upgrade on the second leg. So you will also be in the same queue as those whose upgrade did not clear.

I do not believe that QF will though upgrade someone on the first leg if the second leg cannot be upgraded at that time. i.e. upgrade SYD/SIN but leave SINLHR leg in economy. I do not believe they will do that unless you are on separate flight numbers. So you will have that benefit - happy to be corrected there.

I echo Dave's comment that the upgrade costs are terrible, but if you are points rich and cannot get an award seat then it is a good use of points. Or the other way to look at it is that awards are so cheap being just over the upgrade cost ;-)

KF