Hi Icewing726,
Welcome to the Mattress Forum! 
I would be cautious with the Dormeo mattresses and make sure that you find out all the information in this article about all the layers in the mattress so you can compare them to the durability guidelines here to make sure that there are no lower quality/density materials or weak links that would compromise the durability and useful life of the mattress. I would avoid any mattress where this information isn’t easily available to you from the store that sells it. Their spec sheet doesn’t contain any meaningful information that would be helpful to you because it’s missing the density of the foam layers which is the information that you really need to know.
There is a bit of information about the previous versions of the Dormeo Octaspring in post #2 here. Some of their previous mattresses have used some better quality materials in the past, but I would make a careful “value judgement” when purchasing an item like this.
I’m not sure what you’ve read since you found the site but just in case you haven’t read it yet … the first place to start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps more importantly know how and why to avoid the worst ones.
Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort”, firmness, and PPP that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well he will sleep), durability (how long he will sleep well), and the overall value of a mattress compared to your other finalists based on all the parts of your personal value equation that are most important to you (including the price of course and the options you have available after a purchase if your choice doesn’t turn out as well as you hoped for).
Regarding reviews, while other people’s comments about the knowledge and service of a particular store or business can certainly be very helpful … I would always keep in mind that you are the only one that can feel what you feel on a mattress so I would be very cautious about using anyone else’s suggestions, experiences or reviews on a specific mattress (either positive or negative) or review sites in general as a reliable source of information or guidance about how you will feel on the same mattress or how suitable or how durable a mattress may be for you. In many if not most cases they can be more misleading than helpful because a mattress that would be a perfect choice for one person or even a larger group of people in terms of “comfort”, firmness, and PPP (Posture and alignment, Pressure relief, and your own Personal preferences) may be completely unsuitable for someone else to sleep on (even if they are in a similar weight range). In other words … reviews or other people’s experiences in general won’t tell you much if anything about the suitability, quality, durability, or “value” of a mattress for any particular person (see post #13 here).
I’ll be interested to know if you find out further information about this mattress.
Phoenix