I'm a big fan. I bought this one off Amazon back in 2011 and it is still holding up great.
http://www.amazon.com/Sleep-Innovations-Shiloh-12-inch-Mattress/dp/B003CT37L0/ref=lp_10063230011_1_1?s=home-garden&ie=UTF8&qid=1459033626&sr=1-1My original expectation was that even if it "got lumpy" or whatever after a few years that for 1/4 the price of the name brand, I'd just order another. However, it has held up remarkably well. I like a firmer mattress and the 12" is quite firm. I bought the 10" for my parents not long after I bought mine, and it's a bit softer.
One complaint people have with memory foam is that it holds in heat. I DO NOT like to sleep hot, so am sensitive to that. The only times I've ever had a heat problem is back at the old place (no air conditioning) when we got some of our very few 90 degree days (actually nights, because we had hot winds blow off the mountains in the evening during those times). Now that I have AC, no problemo ever.
It does somewhat mold to you (not like a perfect mold of your body, as commercials sometimes show). It is quite comfortable. The one time I found a downside to it was after I got back from the hospital after having an abdominal operation. I tried to get out of bed (getting in was easy) and it was NOT fun. Not as easy to get out of as a conventional mattress. Normally not a problem, but that time it literally took me 30 minutes of inching my way to the edge before I could get out, and the last movement of getting up was... excruciating. After that I slept in my recliner for the next five days.
If you shack up with someone, it also doesn't transmit movement as much as a conventional mattress. This is great for sleeping, but some people don't like it for non-sleeping activities.
Anyway, two thumbs up from this guy. It's what I'm sticking with until they invent something better.