Actually IREX ebook reader are designed as book reader not as book writer
So:
1) E-Ink display not designed for writing and refreshing screen takes a while
2) Overall system not designed for writing: virtual keyboard useless
3) A battery will be drown quickly, because, by design, most time a device should be in a sleep mode.
Sincerely
Yura
P.S. I also started with this Idea, but quickly realized that as ebook reader it is good device, but for other better to use a smart phone