Just read this very interesting article on the Blog at Kobo, which covers some of the stuff mentioned in this thread, including color e-ink readers.
eReader vs. Tablet: which screen should you be reading on?
The problem it seems to me with folk that have the view leebase does, is that they are purely going by their personal experience, which doesn't really cover long term effects or the various things that are happening that aren't all that obvious, but happening never-the-less.
The science seems quite clear to me, that an e-ink reader is better for the eyes of everyone, even if that is not visibly obvious to a user. And I say that as someone who quite happily uses a 10" Samsung tablet for ebooks that require such.
And as I said earlier, the mind boggles that Kobo brought out standard size color e-ink readers, where you truly only get a minimal benefit of color. Why the hell didn't they, brink out the 10.3" Kobo Elipsa in a color version, where the benefit of color on that device would be so much more and a really good selling point.