Having used it now for a while, hunting and competing, I find the MIL/MOA combination VERY compelling.
For ranging targets, for some reason, I am still MUCH faster with the MIL measurements above the line. But then for holdovers and holdoffs, it makes so much more sense to use MOA marks with MOA turrets. Given that, in competition and in hunting, that I don't find I have enough time to dial all the time, it's good to combine the two -- dial for gross holdover or holdoff, and then use the reticle for fine tuning.
So, now I have a Leupold and two S&Bs converted, and two more S&Bs on the way.