I looked at it and I think it is kind of cheap and chinzy looking. All the installations looked like hack jobs, whereas an OWB installation is much "cleaner". Also note the lack of insulation on the ductwork, especially the return air duct.
On the system design, a 425 CFM blower is really not enough airflow to move 100,000 BTU's. Most furnaces of that output have at least 1,000 CFM's. The page makes extensive reference to return air systems, but can such a small blower efficiently move enough air through a long return air system to work properly? I would rather have a REAL blower that can actually build some static pressure and push the hot air through a real duct system, something the website explicitly does not recommend. Also, it does not have a grate or ash pan, so all the ashes must be removed by hand, and if they build up they interfere with the furnace operation, a particular problem wth something that is supposed to burn for 8+ hours.
I think you would be way better off ordering a Daka add-on furnace with the big 1320 CFM blower, building a little insulated shed around it and running insulated supply and return air ducts to it from the house. That will give you a system that is more aesthetically appealing, can connect into your home's existing ducts and will outperform this system for aout the same cost.
Lastly, I find it unprofessional to have personal family content and religious links on a business website. If you are into you're faith, that is fine, I am not. Please keep your personal and professional lives separate.
And that is my $0.02.