I’ve used them in the past. The plastic is thinner than pvc cages, but still sturdy due to the way they are molded. I never had any issue heating them. Depending on what species I was keeping in the cage,
I used either UTH or heat lamps. This was prior to me discovering RHP’s, which would have been light years better in my opinion. The only issue I did have was keeping humidity up because the ones I had came with fairly large screen vents plus I was using heat lamps. This can be overcome by covering some of the vents and using a good substrate that holds humidity. I will also add that you can’t put anything heavy on top of them as this will cause the sides to buckle a bit.