Yep, iDevices are overkill for reading, and more importantly, not good for that purpose. Stick with an eInk reader. Don't like the Kindle, look at the NOOK (I have both the classic and the new "Simple Touch" reader which is really nice) or the Kobo (the Simple Touch and the Kobo Touch are nearly the same device). They use the industry standard and don't tie you into a single vendor.
As for the tie-in thing, I dislike it on principle, but in practice it makes very little difference. Thanks to Apple there's no price differentiation on the vast majority of books, availability is nearly the same for all vendors, and as long as we have DRM you always have the danger of not being able to read your book in the future. So the tie-in "problem" is only slightly worse for the Kindle, where the DRM is proprietary and Amazon won't license it out.