I usually tend to fall asleep when i read in eink. Its like a sedative..so so slow that it puts me to sleep.
I use ipad with a matte screen protector and at min brightness.
For pdfs, I use goodreader on ipad and i can flip through my pages as good as a real book at min brightness Or I can use stanza, which renders pdfs in black in night mode. Almost as good as it gets.
Since i have a the habit of suddenly remembering something i ought to check, i can shift out of the app and open a browser..check some stuff and come back again. All in a few secs. Eink..makes me sleep.
Eink has its place..but for me its like a safe sedative...