I've seen these but haven't had a chance to use them - the edges looked pretty sharp and unergonomic which worries me since I tend to read for >1h at a time. The price was also not significantly better than a tolino for slightly lower specs across most axes, but maybe I wasn't looking in the right place. (And technically, it is tied to a store, but it does seem fully optional.)

I have little interest in installing custom software for an appliance, so it would need a very good hook if the default reader is so bad most people are replacing it.