I don't think that just because a plastic container won't physically melt all over your food (like polystyrene or polyethylene), it's necessarily safe in the microwave.

A few years ago DH brought home some polycarbonate Tupperware containers that were labeled as microwave-safe. Not knowing any better, I tried that once. It didn't melt, not one bit, but it released fumes that were so noxious I had to evacuate and ventilate the kitchen.

Just because polypro doesn't do either of those things, I'm not totally convinced that I can rely on its safety. Yes, I microwave it - with reservations, same as I still get my water in polycarbonate jugs. No, I don't trust either one of them.