EInk Kindles can't really do email, or twitter, or skype or angry birds. Right now I tote around three devices (four when I haul my laptop.) A smaller iPad means I get rid of the Kindle and the iPod touch.
I have used the GoodReader app on iTouch/iPhone and read about 10 MB of txt files so far. (The 2001 triology, all Stainless Steelrat, the Red/Green/Blue Mars triology, a lot of Heinlein, the Ringworld triology)
I find the iDevice very easi to read on. Perhaps e-ink is even better.