Calling this an "open letter" seems like an abuse of the term. Or else they're taking themselves way to seriously.
I'm not really seeing the point in this post. I use instagram almost every day and I'm not really seeing a difference between their revision and what I see on my screen.
This isn't to say that it isn't different, perhaps drastically, but I'm not seeing any sort of improvement.
What Instagram needs is a hand-stitched banner and frilly paper cut-out borders between photo metadata and photos, and also pastel buttons? Uh, ok.
this seems to be a new trend, redesigning instagram. Interesting how the design changes are purely visual. I'd make one actual interaction design change to Instagram, personally: When you're choosing the filter, swiping on the large image itself should change the filter, not just swipes on the narrow row of icons at the bottom. Currently there's a huge interaction dead-space in the middle of the screen. I always find myself swiping the middle trying to change the filter...