The only ones I slept on were the old ones. My best friend had one with no heater, just the pad and no support except for a wooden frame. It was no fun when you were drunk. You just sloshed around. And God forbid if the pad moved. You'd wake up freezing.
Now I've seen everything related to threads haha. Back at our old place we had no guest bedroom and my buddy and his gf had to stay over. Got the brilliant idea fueled by a bottle of whiskey to fill an air matress with water (in lieu of the air comp on my truck and and a capable set of lungs). They loved it for the comfort factor.
Then they woke up sober and frozen haha.
Never had an experience with an actual waterbed but I imagine it would be therapeutic on your own. (I imagine too much motion transfer otherwise)