I skimmed a consumer-feedback site and made some observations:
* All mattress designs have unhappy customers. There is no single mattress that satisfies most people.
* As a feature, the pillowtop attracted a consistently high degree of negative feedback - good in the showroom, lousy to live with. They're particularly problematic in a hot climate, where people found them overwhelming.
* Durability of modern mattresses is highly suspect. Some deteriorated within weeks.
Some people like memory foam, but many don't. You really want to try it out before committing to it.
Latex is pretty much the opposite of memory foam: fast-response instead of slow-response. Most people like latex, and it's very durable, but there are some negatives:
* It's incredibly expensive
* It's hotter than an innerspring mattress
* You need to protect it from moisture (same for any mattress, but after paying several thousand dollars, you really want to protect your investment).
I'm particularly enamored with Will's mattress. The highest quality foam possible (latex) on top with layers of increasingly stiff foam underneath - really should have been laminated properly though, as he discovered. I'll definitely consider that for my next mattress.
There are two main types of innersprings: interlinked and pocketed.
* Pocketed are usually more expensive, more compliant with body shape and best at minimizing one person's movements disturbing another. Nevertheless, some people find the available products (eg. Simmons Beautyrest) too soft.
* Interlinked has subcategories, the main thing to watch is the amount of steel in the mattress, as evidenced by coil count, turns, gauge etc, or probably just price! A mattress can still support someone in the showroom while using fewer and/or thinner (but stiffer) coils - not a good long-term proposition.
The biggest problem is the laminated foam layers on top of the springs. This is where you will find the main difference between cheap and expensive models. Unfortunately, the difference is durability, and you can't determine that in the showroom.
We currently have two Simmons Beautyrest mattresses (one on a box spring base, one on slats), a Sealy Posturepedic (on slats), a custom foam mattress (on more foam!) and some random innerspring (also on slats). Unfortunately, we have observed a direct relationship between price paid and longevity. Eg, the Sealy cost half as much as a Simmons and needs to be replaced after 6-7 years. Based on experience, I expect to get 10-15 years out of the Simmons, and we only got about 3 years out of a mattress that cost half as much as the Sealy. Sadly, Simmons mattresses have been declining in quality for years, more so recently according to user feedback.