While pocket coils help, they barely isolate motion at all. The only mattress to truly isloate motion is a viscous (memory) foam product.

I have a latex mattress where each half of the matress is built up individually and even this is not anywhere near as isolated as memory foam. If I swap out the last 2" topper which covers the whole mattress combo with memory foam, then it approaches the isolation I used to have on my previous memory foam mattress.

If looking at memory foam, don't buy into a cheap product because the lower layers of non-memory foam are going to break down quickly, leaving you with a terrible sleeping mattress in no time.

My ultimate right now is latex with a memory foam top. The latex can be combined in layers to suit an individual's needs. I'll never go back to a spring mattress again. I haven't found any name brand that last more than a couple of years at any price (my last one was over $3000). By "last" I mean feel as good two years on as they did the first week, even with regular flipping.

I've heard good things about air-bladder mattresses like the select comfort, but I don't have any experience with those myself. Have only ever spent serious time with traditionally sprung, pocket coils, regular foam, memory foam and latex.