I think that the ViewMaster is a very successful novelty-based toy. But as far as a serious display device, I'm comfortable calling it marginal. That nobody can name their nearest competitor is a sign that it's not a big market.

If the desire for a 3D TV experience can be overcome by casual viewing habits, then that's a sign to me that the value delivered is quite low.

That certainly matches my experience. I found 3D movies a pleasant novelty, but after a couple times it wasn't something I would pay extra for. That's in sharp contrast with, say, color. Or theater-quality sound, which I went out of the way to get for my home setup and make sure is properly working whenever I watch something I care about.