I was first intrigued, but when I saw the price I couldn't really see it being all that useful. It is possible to buy a 4K display with a similar 150dpi resolution for less. So the only advantage I can see here is lower power consumption?
And readability. And only using power when making updates. Using a max of 2.5W instead of 100W is a big deal. You can now power a monitor from your laptop or phone. Also, think about how things tend to work in the electronics industry. DVD players were $1000 in the 90s.
I'd still like a screen like this though. I gathered I can convert my old Kindle to an external screen with some custom firmware, I might do that.