This is a hit or miss product, as are most therapy items for kids with autism. Some kids like the feeling of being embraced; it calms them down and helps them sleep better. For the kids who struggle with sensory defensiveness, weighted blankets may help, or they may send the children into a torrent of screams and fists and feet.
The best thing to do is to introduce the blanket slowly. Some of these blankets come equipped with pockets and varying amounts of weight such that the weight starts out really light, and over time parents can build it up until the children are able to sleep with a fully weighted blanket on them. The blankets can act as lap blankets at home first, allowing the child with autism to touch it and become accustomed to it before it’s lain over them in bed. They aren’t so heavy as to disallow a child from rolling over in bed, but are heavy enough that it discourages them from shoving the blanket off and getting up.
Kids with weighted blankets do sleep better. They don’t get out of bed quite as often, and they are calmer. They help children self-regulate bed time and sleep, which are both really important for them, as well as the parents.