Hi pgtop,
As you mentioned when you make a purchase at Costco and you don’t know the specifics of the mattress in terms of quality or how it feels and performs you are really rolling the dice and hoping for the best and relying on their great refund policy as your safety net if you make the wrong choice (and then you can just start all over again).
You can see some of my thoughts about the Ara and Sleep Science (and the possible inaccuracy of the Costco listing) in post #2 here.
As you can see in post #13 here … reading reviews is not the same thing as mattress research and other people’s experiences can be very different from your own (and are not generally a good guideline to follow). Most people who write reviews don’t include enough information to make the reviews that meaningful (such as their body type or sleeping position) and in most cases they have little knowledge about the quality of the materials in the mattress they purchased (and often mistake their comfort for the quality of the mattress).
Having said that … you can sometimes glean some information about how a mattress feels to the '“majority” of people if there is a clear enough pattern to be able to tell and this can be helpful if you fit the “averages”.
Phoenix