My first “message” !! Hope I don’t screw this up ! Upon reading the info on this site about brand name matresses I would like to know why Seally brand matress was frowned on or you told us not buy one ?? WHY ?? I & other people I talked to thought that was a good brand name !! >> Speaking of of talking to friends one said Seally has not made a matress in 15 YEARS ?? That’s Surprising!!
What do the “WISE” Minds out there have to say about my comment Thanks for any help you offer! 
Hi SAUSAGES,
Welcome to the Mattress Forum! … and I’m glad you found us before you seriously considered purchasing any major brand mattress
There is more about the more recent history of the industry over the last 15 - 20 years or so in post #15 here and post #404 here among many others on the forum that discuss this.
Outside of PPP (Posture and alignment, Pressure relief, and Personal preferences) … a mattress is only as good as its construction and the quality of the materials inside it regardless of the name of the manufacturer on the label and “brand shopping” is among the worst ways to choose a mattress because the name of the manufacturer won’t tell you anything about whether a specific mattress is suitable for you in terms of PPP or whether there are any lower quality materials or weak links in the design (see post #5 here and post #12 here). As you can also see in the guidelines here I would avoid any mattress that either uses more than “about an inch or so” of lower quality or “unknown” materials in the upper layers of the mattress because the comfort layers are generally the weakest link in the durability and useful life of a mattress and a “blind purchase” where you can’t confirm the quality and durability of the materials and components in a mattress (see this article) is one of the single biggest reasons for buyers remorse and the need to replace a mattress much too quickly after a purchase.
I have no idea what they mean since Sealy certainly makes mattresses (although perhaps they are referring to whether they make “good” mattresses which would be a little more accurate). There is more about the most important parts of the value of a mattress purchase in post #13 here that can help you make more meaningful comparisons between mattresses regardless of the name of the manufacturer on the label.
The best place to start your mattress research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choices … and more importantly know how and why to avoid the worst ones.
Phoenix