Hi nomorethant,
I should mention first of all that it may be a good idea not to use an email address for a forum username because there are lots of email harvesters that just love to add them to their spam lists. If you’d like me to change it let me know 
The Serta Cloud 9 is specific to Hampton Inn but it still uses all the same materials (often lower quality) that would be in a similar Serta Mattress (with similar components and foam layers) that you could find in any store. The biggest difference is that it would be more expensive to buy it from Hampton Inn than it would be to buy the equivalent elsewhere … and you wouldn’t have any options left if you bought it from a hotel and it didn’t perform in your home over the longer term as it did in the shorter term in the hotel. You would need to test similar Serta Mattresses though in a store to find the one that you felt had the same level of pressure relief and support (and matched your other preferences) as the Cloud Nine because they don’t provide the specific details of what is inside the mattress so outside of going by feel there is really no way to make meaningful comparisons with other mattresses.
This lack of transparency is by design because hotels are well aware that most people sleep on a mattress that to various degrees have lost their comfort or support (or in some cases weren’t suitable for their body types and sleep positions in the first place) and that most hotel mattresses that are in good condition will be perceived as being better. This creates a new profit center for them (at inflated prices because of many consumer’s belief that their mattresses have some special design or material when they don’t). If hotels did disclose what is in their mattresses, nobody would buy them and they would just shop at their local chain store to find a similar model with similar materials at lower prices and even these (if they are a typical major brand mattress) would generally be poor value compared to smaller local or independent manufacturers.
Overall … I would avoid Serta completely (and all major brands or any mattress where you couldn’t find out the quality of the materials that are inside it). There are hundreds of mattresses that can provide you with similar pressure relief and support/alignment and match your other preferences that use much higher quality and more durable materials and have much better value. Even low quality polyfoam or other materials can feel good in a hotel or showroom but it doesn’t last nearly as long as higher quality materials and the loss of comfort or support is not covered by a warranty.
Without knowing the specs of the Cloud Nine … you would have to test mattresses to find one that was comparable but the good news is that there are so many better quality/value choices available to you.
The most effective way to find the best possible quality and value mattress would be to follow the steps listed in post #1 here which along with the information it links to will greatly improve your odds of finding the best possible mattress for your own unique needs and preferences … and will last you much longer.
As you will see from the linked information … knowing where to buy and who to work with can be even more important than knowing what to buy.
Once you have read some of the general information about the different types of mattresses and materials and know what to avoid … if you let me know your city or zip I’d be happy to let you know of any better sources or possibilities I’m aware of within a reasonable distance.
You may also be interested in reading this post from today from one of the forum members who two weeks ago thought that the best possible mattress was one from the Ritz Carleton and has come a long way in the two weeks since
Phoenix