This is charming. E-paper is such a good fit for ambient data like this — always visible, no glow, basically no power. How often do you refresh the display, and does partial refresh ghosting become a problem over time?
While I'm not sure about the exact e-paper panel model used in this project, in my experience with these small e-paper screens, a full refresh is pretty much mandatory every 10 or so partial refreshes—which is significantly worse than Kindle-level performance. Just about every screen I've worked with suffers from some level of ghosting, and it definitely gets noticeably worse in higher temperatures during the summer. Plus, these cheaper e-paper displays tend to degrade quite fast—after a couple of years, the aging becomes painfully obvious.