I've had a waterbed since I was 3 years old. (I'll be turning 26 next month, so I've had one for about 23 years.)
I'm totally used to it. It can hurt sometimes when the water level gets low or when there's a huge, annoying air bubble in it, but so long as I have it filled and "burped," I have no problems. I also keep an insulating blanket and an old comforter on top as insulation. It's also like a pillowtop mattress pad for me.
In the summer, I keep the temperature low (about 65) and I stay fairly cool. The cool water inside the mattress acts as a kind of "air conditioning" or, rather, "water conditioning" that keeps me cool when I need it.
In the winter, though, it's Niiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii... I can't emphasize that enough. It is so amazingly nice on those cold winter nights. My house is heated by woodstove, for the most part, so the furnace doesn't kick in 'til the temperature drops below 68, so my bedroom is always chilly. But, my waterbed's heater is a nice warm, pleasant 85-90 degrees. Toasty warm and pleasant.
So, I'd have to say waterbeds are my preferred, if only for the amazingness of winter.
Edit: THEY DO NOT CAUSE BACK PROBLEMS!. I'm perfectly fine, and I've been sleeping on a waterbed since I was 3 years old. I've been sleeping on it nearly every single night for twenty three years straight! I don't have horrible back pain at all. The last time I had horrible back pain it was from sleeping on a really crappy regular bed with awful springs and a broken down frame. I have kept my bed well-maintained and have had no problems.
And no, you can't drown in a waterbed unless you're an idiot. There's no waterbed frame that is really water tight. A popped mattress would be a really slow leak (I did it once, slept on it for a couple of nights with a towel over the leak. You would push the water out and all over the floor since there's only a very thin layer of vinyl that is not really all that water-tight anyways, since the vinyl liner is shorter than the mattress typically is.
Even then, you would have to be handcuffed in such a way as to be depressed into the mattress box, which itself is only about 9-12" deep. Your headboard is too high to have you handcuffed IN the mattress area. Being handcuffed to the headboard, your upper body would be lifted slightly up off the bed anyways, and you could pull yourself up since your hands are free but your wrists are not. All those blankets and pillows would suck up a LOT of water.
Finally, perhaps you shouldn't allow yourself to be handcuffed to the bed if you have any inkling that your partner is going to leave you there...
I've had a waterbed for 23 years. I have NO back trouble at all. I also have not died. The few leaks I've had have been easily dealt with by replacing a mattress. They leak, they don't "pop" and the leak is typically very slow, easily slowed with a towel, until you can repair/replace.