I own two. I bought them for crevasse rescue. They don't do much unless the rope stays on the roller. An non 3d attaché would work fine for a hauling system and is quite a bit cheaper. They are awkwardly shaped too.
www.rei.com/product/799043/petzl-ultralegere-pulley?cm_mmc=c>>> I keep this on my rescue oval if I needed to haul a second.
So what is this newfangled iron horse I am hearing about?