Your link is wrong in the initial message (an extra W)
I think the bike has some potential market, but not for me in the current configuration...
But, I do have a few comments. Some of the information may be on your site, but I did not see it on a quick look through.
I would be hesitant about buying the paired spoke wheel with a coaster brake due to the torque applied during braking. If this is indeed a non-issue due to your own engineering or testing results, you should address it on your web site for peace of mind of potential buyers. At least it isn't a low spoke count wheel.
On your web site, in the area helping to guide sizing based on inseam, the word "is" repeats itself in each line.
The frame sizing for a traditional non-sloping top tube seems very limited... Your target market seems to be everyone from about 5' 9" to 6' 1" (probably a little more range, but not much). In fact, the total size range is from slightly below my usual frame size to my upper limit of frame size.
Many riders that would buy based on performance will want to see more on the frame geometry than just the seat tube length.
I assume reflectors will need to be included on bikes that you actually sell, although they are not pictured on the bike on the site. You may want to include them on the site's pictures to avoid potential liability issues.
Also, many adult bikes with coaster brakes have traditionally had a front caliper brake since the front brake is very useful for panic stops. It would be nice to at least have it available as an option, or at a minimum ensure that the bike is set up to easily add aftermarket brakes (and let potential buyers know that the bike is ready for brakes if desired).
I would personally like to see a model set up for use with an internally geared hub of some sort for those of us that live among hills. I know this goes against the simplicity element, but just in case you branch out.
Good luck on your endeavor.
EDIT:
Just looked again at the sizing... I remembered wrong. 52-56 seems a little small It must have a pretty high BB. Anyway, I did notice you do have a little more info on sizing as well, like top tube. You may also want to include angles, which mean nothing to me, but some people care about such things.
Again, looks like the start of something good.