I have no aversion to using them if the animal is actually going to use it. I have a couple of skulls in with my snakes, because they look okay and act as a hide.
My terrestrial tarantula enclosures are far too shallow for skulls. Because this species likes to be more off the ground, she is the only one that I have in a glass exo-terra with the front doors.
She has moulted inside it once and basically ignores it. It would be much better in one of my snake enclosures. Now that she is full grown, maybe I'll replace it with another big piece of cork bark.