Hi jdubya,
Specialty sleep (memory foam, latex, airbeds, etc) is certainly growing faster than other market segments but traditional innerspring / polyfoam mattresses still account for the large majority of mattress sales (almost 2/3 of mattress sales).
Once you have eliminated innersprings as a support system though … then deciding what type of foam you prefer in the support layers (generally latex or polyfoam because memory foam isn’t suitable for deep support layers) and the comfort layers (polyfoam, memory foam, latex) and of course the specific mattress that will provide you with the PPP (Posture and alignment, Pressure relief, and Personal preferences) that is suitable for you are still an important part of your choice.
No matter which type of foam you prefer … choosing good quality materials is important forthe sake of durability (both low and high quality foams can feel very good in a showroom and you can’t feel the quality of a foam).
Both the Sealy Optimum (see here) and the Serta iComfort series (see here) are not good value and neither one discloses the specific quality of the materials they use in their mattresses (although some alternative sources have made some of them available). Smaller manufacturers like Dreamfoam use the same or higher quality materials in every budget range and have much better value. I would keep in mind though that latex (like the Bamboo Bliss and Aloe Alexis) and memory foam mattresses (like the iComfort and Optimum) are very different materials with a completely different feel and response (see post #2 here).
I certtainly wouldn’t go by reviews because each person’s experience on a mattress is very subjective and may have no relationship to what you will feel. The “best” way to choose would be personal testing on similar mattresses that were available locally and if that isn’t available then the next best way would be with more detailed conversations with the retailer or manufacturer who can use “averages” to help you make the best possible choice. The options you have available after a purchase may also be an important part of your personal value equation and both of these have comfort exchanges that allow you to exchange layers if you make the wrong choice which reduces the risk of an online purchase. In effect it allows you to do some testing using your actual sleeping experience.
Their memory foam mattresses are the ones that are usually compared to some of the Tempurpedic line but their latex mattresses are a completely different animal.
They could certainly let you know how their memory foam mattresses compared to the Tempurpedic line (and could probably give you some insights about how they compared to the iComfort line as well in more general terms) but again their latex mattresses wouldn’t be comparable to either.
The “best” approach IMO would be local testing on similar mattresses (latex / polyfoam hybrids if they are available locally) so you are familiar with the general feel and response of latex combined with more detailed conversations so you could make a choice that was as close as possible to your ideal.
Phoenix