I see that this older thread got bumped but I'm not currently advocating a mash out infusion because I found that a no mash out, double sparge produced the same or better efficiency as long as your sparge temp was elevated to about 180F or whatever temp it takes to raise the grainbed near 170F by the second infusion. The method is described at the bottom of this page:
www.suebob.com/brew/allgrain.htm
When I posted this thread a while back, I was limiting my sparge infusions to 170F so it makes sense that a hot mash out infusion would boost efficiency. I also think that buying a mill and cranking it down made a difference.
The caveat is, you'll actually lose efficiency if your sparge infusions are less than 1qt per pound. This can easily happen when you do a MODS on a big beer.