The downside is that eInk currently only supports black-and-white and turning pages is roughly only as fast as turning the page of a book.
Also, battery life is counted in days (and sometimes weeks) and not in hours.
E-ink Kaleido with 4096 colors at 100 ppi are available commercially since past few weeks
https://www.youtube.com/watch?v=mqiCOheb1jo
The downside is that eInk currently only supports black-and-white and turning pages is roughly only as fast as turning the page of a book.
Also, battery life is counted in days (and sometimes weeks) and not in hours.