Insulation Substitute

Just a quick question..... Have others used 1" or 1.5" HVAC rigid ductboard a substitute for 703/705 insulation with much success? I have used it in my personal studio designs due to a cost factor, as it is also compressed insulation, but am asking for professional opinions based on personal experience with both. Thanks. 8)

Haven't actually used it as yet, but spec-wise I saw a couple of versions that are virtually identical to 703/705, except better because the surface is more durable. I'm not sure what the different surface does to grazing incidence (as compared to straight on, 90 degree incidence) Anybody else?