Hi cbmd81,
I’m glad you asked about them and you are the first one to mention them on the site 
Leesa is a new startup and like Casper and others are one of a new “breed” of online companies that are selling “one size fits all” mattresses that are doing their best to convince consumers that a mattress can be “universally comfortable” for everyone.
Of course anyone that is familiar with the industry or with mattresses in general knows that this isn’t possible and the reality is that any single mattress will be the “best” match for a relatively small percentage of people, a “good” match for a little larger percentage, and a “OK” match for a larger percentage yet. For those where the mattress isn’t a “good enough” match they all have a great return policy.
Most of them are using their marketing background and experience to tap into the overall negative consumer sentiment about the mattress industry and are attracting many consumers that “want to believe” that everything on their site is true. For the most part they are portraying themselves as being a simple solution to all the problems in the industry. One of the common themes that most of them talk about on their websites is that they cut out the “middle man” but few of them (so far) are actual manufacturers with their own factory so they have a “middle man” making their mattresses.
They are often more focused on marketing than they are on mattresses and they tend to be most attractive to consumers that don’t realize that some of their claims are questionable or that don’t want to take the time to do more detailed research to find better quality/value mattresses that may be a better match for their specific needs and preferences. Some of them use various incentive discount schemes that turns their customers into salespeople and these customers will often post on various websites all around the internet with a link to their discount code that provides a new customer with a discount and also gives them a rebate for every new referral. In many cases these customers will post raving reviews about their new mattress before they have even slept on it to try and get as many new referrals and referral bonuses as possible and I have seen some sites where there are dozens of people one after another all linking discount codes in the hopes that other customers will click on their link. In other words … these customers will often say whatever they believe will make them the most money rather than providing honest reviews of the mattress itself. Of course these types of referral marketing systems are built into the cost of a mattress.
While many of these mattresses are “better than average” quality/value compared to most mainstream or major brand mattresses … they certainly aren’t “luxury mattresses” and with a little more research most consumers will find that there is often better quality/value choices available through many smaller manufacturers or retailers across the country or online where they can choose a more customized mattress that is a more suitable match for them in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) and that use higher quality materials in their mattresses in a similar or even lower price range. 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.
In the case of Leesa … they share common ownership with http://brandjourney.com/ which is a marketing and consulting company that specializes in new startups and building brands and brand awareness.
I had a fairly extensive conversation with them a few days ago about their company and their mattress. All the people that are listed on their site are marketing people but they told me that they do have someone that is a “mattress person” that is involved with the company that is part of a larger multi-generational mattress manufacturer that was responsible for the design but they weren’t comfortable telling me who they were or the company they are involved with so they are a “hidden” presence behind the company. NOTE ADDED: The "hidden partner is Jamie Diamonstein who is part of the family that owns Paramount Mattress. He has been making mattresses for several decades and decided that he wanted to go out on his own and build a company and a mattress that was more transparent and creative.
I also talked with them about their mattress and you can see the specifics of the materials here.
The top 2" layer is a 3.75 lb density high performance convoluted polyfoam which like many of this newer type of higher density polyfoams that are now on the market is a high quality material designed to have many of the properties of specialty foams like latex or memory foam but without the slow response of memory foam (see posts #2 and #6 here).
The next 2" layer is 3 lb memory foam which is a lower density than I would be comfortable with in a mattress in this price range and would be a potential weak link in the mattress in terms of durability IMO.
The support core is 6" of 1.8 lb polyfoam which is a good quality material that is suitable for a support core.
Overall … with the 2" middle layer of 3 lb memory foam … I would be somewhat cautious because there are other mattresses in this price range that use higher quality and more durable materials in their comfort layers that are in the same or lower price ranges (the comfort layers are generally the weakest link in a mattress in terms of durability). While this mattress would compare well with many mainstream mattresses … on a site like this where the members have access to a much larger number of higher quality/value choices and are more informed about how to make more meaningful comparisons … they don’t compare quite as well to some of the other options that are available.
Phoenix