Huh, that's actually pretty clever, and would make conversations easier if you're flying with people you know, since you'd be looking at them.
The reason this saves significant amounts of space (which isn't explained adequately in the article) is that the shoulders are generally the widest part of a person, and if you configure the seats so that you don't have shoulder-to-shoulder contact down the entire row, you can fit three seats into a narrower space. It doesn't matter at all if my shoulder overlaps with the legs of the person next to me, because they aren't at the same height level, so our seats can be closer together.
It's pretty clever, unless you realize the people we want to put in those seats are actual humans, who might not be thrilled to be packed like a sardine, staring into the eyes of a stranger for hours at a time.
I've been on a fair number of train rides with group seating, and I've never experienced a problem with it. That's actually worse from your point of view because there's someone directly across from you, not just diagonally across. It's preferable if you're traveling with people you know, and if you don't know them, you simply look at whatever you're reading (or end up talking to them). People tend not to stare directly off into nothing for long periods of time when they're in cramped confines; they do something to occupy themselves, like read a book/magazine, or they close their eyes and rest.
In the typical groups seating on trains, you are however seated far enough apart that only rarely do you have to touch the feet of the other passengers. In the hexagonal seating you are spaced such that if you lean back, the natural resting place of your hands would be the wrists of the person opposite you.
I was expecting a few inches shaved off the seat depth and came here to say 'every single time it's "most passengers won't notice a difference" and then fast forward 30 years and the cushions are 1.5" thick and everyone's basically standing up'
You would get better packing efficiency if the "chairs" were just straight boards you strapped people to and put them on shelves. You'd also have the advantage of the people in the top rows shielding the bottom people from radiation.
The article mentions that the hexagonical packing had been suggested starting from 2007, and it is essentially used in practice[1], but not with quite the same emphasis on "packing" as the OP post.
They also promoters of the 2007-hexagon also mention the privacy issue as their main guess at why nobody has used their seating.
If the shoulders are the problem (because they are the widest part of the body) why not putting every other row slightly ahead? Or slightly rotate the chairs from the side rows outward?
The reason this saves significant amounts of space (which isn't explained adequately in the article) is that the shoulders are generally the widest part of a person, and if you configure the seats so that you don't have shoulder-to-shoulder contact down the entire row, you can fit three seats into a narrower space. It doesn't matter at all if my shoulder overlaps with the legs of the person next to me, because they aren't at the same height level, so our seats can be closer together.
Backwards-facing airplane seats are also safer, but aren't standard for other reasons: http://www.airspacemag.com/need-to-know/are-aft-facing-airpl...