Hi pickamattress,
Post #13 here has more about the most important parts of the value of a mattress purchase.
The first question I would ask yourself is how confident are you that this mattress match your specific needs and preferences in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences). When you can’t test a mattress in person then you would be completely dependent on the knowledge and experience of the retailer or manufacturer you are dealing with and most of the customer support staff at Overstock aren’t particularly knowledgeable about “matching” a mattress to different body types and sleeping positions and are more interested in selling you whatever you are willing to buy than they are helping you to choose the “right” mattress. This means that the return policy would become a more important part of your decision to offset the risk of making a “blind” purchase and this mattress isn’t returnable once you have used it.
The next most important part of your purchase is making sure you know the type and quality of all the layers in your mattress (see this article) so you can compare them to the guidelines here. In this case the description doesn’t include the information you would need about all the materials to make an informed choice and I’m not so sure that the “better than latex” material is latex at all … synthetic or otherwise. I would want to see a copy of the law tag to see if it includes latex in the materials and I would want to know the specifics of all the layers and materials in the mattress.
Vivon is also one of the Zinus brands that also includes Night Therapy, Spa Sensations, Keetsa, and many others. They are all Chinese made mattresses that tend to use some lower quality and less durable materials in their mattresses although to their credit they are CertiPur certified. A forum search on Zinus Vivon (you can just click the link) will bring up more information and feedback about them.
I would also be aware that these mattresses are being liquidated and are no longer being made (they are no longer on the Vivon website here). This means that at best they are just clearing out old stock but at worst they could be comfort exchanges or warranty returns as well. It also means that they have probably been compressed for quite some time in shipping and storage which could also lead to durability issues (see post #6 here) so I would want to find out the manufacturing date on the law tag as well.
Overall I would say that from every perspective … this would be a very risky purchase and you would have little to no recourse if the mattress either wasn’t a suitable match for you in terms of PPP or if there were durability issues with the materials.
It certainly isn’t a choice that I would consider.
The first place I would start your research is the mattress shopping tutorial here which has all the basic information, steps, and guidelines that you will need to make the best possible choices in any budget range … and know how and why to avoid the worst ones.
Phoenix