The biggest reason for making this, for me, is that it would be a great modular approach to problem I face a lot. I want/need a display in my project, but I don't want to eat up precious battery life using an LCD. Something that just turns on to update would be invaluable as an internet appliance, such as a grocery list that you can update with your smartphone when you notice something you need. Conversely, using this type of display with a desktop GUI like in the Pi would yield some savings of electricity. If you were just reading text, perusing datasheets, or typing notes, screen updates wouldn't have to be that frequent, saving energy on the display budget. Also if just a small area of the screen is changing, this part can be re-written only, requiring only a portion of the energy required to change the image on the whole display.

My ideal vision for this project involves the e-ink screen, a battery (maybe start around 2500maH and see what that does for me), small keyboard (prolly about 80% size, but otherwise a real keyboard), USB broken out for connecting a mouse and/or wi-fi, speakers of some kind (although maybe just leave the headphone port broken out too, Idk yet), solar panel on the backside of the screen so you can run it off solar power in the coming post-apocalyptic wasteland. Back of the napkin calculations say that the Pi Zero or A consume about 80maH when idle. The e-ink power driver board consumes about 50mah in standby and 100maH when updating the screen. I'd say it would be safe to say 180maH should be about average for this thing. That means a 2500maH battery should last about 12 hours, accounting for losses in conversion and that it will be making 5 volts out of a 3.7-4.2 volt battery. The solar panel I'm eyeing (as much for the output as the size) puts out about 330maH, so this would be perfect. Get about an hour of solar charge and run the device for more than an hour and a half. This is the solar panel I'm thinking about using:

https://www.adafruit.com/products/200

Who would use this thing? And how? For me, the laptop version would be great for camping, as I do a bit of writing on the computer, and it would a great low-cost typewriter. I already take my stock kindle camping with me because I have a library of almost a thousand books in seven ounces. Now that the full Arduino IDE is supported, you could also program an Arduino with it. I could do this while going out and standing in lines to pay bills and such, and get at least some work down instead of playing Sky Force on my phone. It would be great for taking notes in university, and with Open Office you could save it in formats recognizable by your phone or your other computers. It would be a great media player, although just for mp3s, I don't know how movies would fair. The modular aspect of it means that you would be able to write custom software to display whatever you wish, like a calendar, a webpage, or information from sensors to make a good sunlight-readable display. What would you use one for?