I've heard the same complaint about pillowtop mattresses.
We have a regular mattress. It was a company that makes them in Columbus, OH when we lived there so it's been a good one. But we're going to have to replace it soon...guess it got wore out or something.
Anyway...waterbeds are bad for backs, I've heard and a hassle. I'd say go simple, but get something with good support like a Sealy Posturpedic. Comfy to sleep on and works for me when having sex.
