I've been looking at getting an e-reader in the last few days, and the Xteink X4 is one of the ones I considered. I think it's probably too small for my intended use, but it's cool that people are tinkering with it like this.
But for those that want that, I guess this is a cheap version?
I personally hope this could drive more sales for those who don't necessarily want an ereader (or already have one) but are interested in tinkering with it (I doubt anyone looking for gaming or messaging will pick it, seeing it's still more expensive than a proper Android phone), and thus lower the price of future models for everyone.
There's probably some niche where ridiculously long battery life (plugging a small solar panel will effectively make it self-sufficient) and sunlight readable screen with very basic apps would be welcome.