Well thought out post (and good looking too).
I've had some similar ideas floating around for a while now and I'm glad to see I'm not the only one :o)
It seems like there is a lot of backlash lately against media (ie. videos, sound, images), but I believe that these things can be incredibly compelling when used in the proper context.
Good writers are good writers, but without a platform to deliver that content supplemented with great pictures, video, and sounds... it seems like a waste of the medium.
This is a thoughtful post. I really enjoyed it.
A thing that you didn't touch on much—and is probably also a reason why we haven't seen many great, flexible experiences like this—is the variable of the user. In a magazine, you get to deal with fixed dimensions. "Snow Fall" works best at a certain size and aspect ratio and on a certain device. I think they were able to build something so impressive by limiting the scope.
The important thing that "Snow Fall" and your post point out is that the writing is at the center of the story, not the frills. Infographics, The Daily and others fail(ed) at this. The best magazines still have the best writing, coupled with visuals that do the story justice.