I tried one given by DH to me (can't remember brand). It was mid-weight, sized for someone my weight etc. and filled with small glass beads I think. It had a bamboo cover which was supposed to keep me from overheating, a big deal for me.
I tried it three nights before giving up. The first night was very comfortable but seemed heavy on my legs especially. I woke up the next morning having slept the night through but my whole body felt extremely stiff; evidently I didn't move much during the night. It took a few hours for the stiffness to disappear. The second night was a bit better but I still felt some stiffness. And the third night was no different. We returned it.