The SM3 reminded me of
autostereograms, you remember, those pictures with dots that you had to focus on to see the 3D picture. Some people saw them, and when you see it, it is much more 3D than a regular picture (but devoid of color and the other details, of course), but there were many people that I know that hated those, but couldn't see the image ("all I see are dots, these things are stupid"). Here is the concept: "In order to
perceive 3D shapes in these autostereograms, the brain must overcome the normally automatic coordination between
focusing and
vergence."
Of course, this is not a perfect analogy (or even a great one), I do see some parallels. And once you could see the image in a particular picture, subsequent viewings resulted in the image appearing much more readily. So, maybe all the SM3 differences are in the brain. Not that people will agree, but I thought it was interesting enough to share.
Happy holidays to all the SM3 supporters, SM3 detractors, and SM3 neutral people!