When I think of waterbeds, I equate them with a big pain in the ass...my lower back, to be exact. I've slept on waterbeds several times in the past, and after each extended period sleeping upon one, I'd awake with an increasingly sore back and memories of bad dreams about wetting the bed.
Sure they were fun while awake for obvious reasons, but over hours of unconscious sleep, the old school water bed was a poor supportive surface for the spine. And getting out of one of these older waterbeds was like a core exercise of frustration; you'd have to swing out your legs first, and then push down to create a wave, then wait for the reflected wave to return to use it springboard out of bed...sometimes with cannonball effects. And darn if it wasn't a pain to fill that bed's bladder using a hose into the bedroom or repair a leak.