One reason I have been sleeping in a waterbed since 1978! I had a full motion when I bought if and hadn't changed it out until 1989 when we went to dual mattresses and heaters plus a pillow top that unzips to get to the water mattresses. They both are semi-motionless and very comfortable. We tried a Select Comfort (now called Sleep Number) in the late 90's but couldn't stand how hard it was no matter how much air you put in it and took it back before the 30 day trial period. I still can't believe how much mattresses sell for and how often they recommend you to change them out!