Will not give a square cut above in materials much above 1"
I've not tried to use the blades on wool type insulation yet but on foam type (Kingspan, Recticel etc.) the blade gives a nice smooth, dust-free cut but with thicker sheets (2"and above) the blade bends and doesn't give a square cut. Fine if you want wedge shaped insulation but not much use otherwise.
Used to cut block foam from Dunelms - used on high speed with scroll and cut really cleanly through even near the edges. Far better than hacking through with a bread knife!