Just got a Kindle yesterday, for a project I'm doing. I am not impressed.
This thing has horrible readability in low light (why not add a backlight?), annoying reverse blink whenever you change pages, and relies too much on the small and virtually unreadable keys on the keypad. Along the same lines, the interface to the Amazon Kindle store is in extremely small, unreadable, and unresizeable text. (As you can probably tell, I'm big on the unreadability thing, especially as my eyes age -- small type doesn't work well in my apparently dark and dreary world.)
I'm not tethered to any particular container; I care more about the content than how it's delivered. But the Kindle makes reading somewhat less enjoyable, at least to me. Bah.
But that's just my opinion; reasonable minds (or people with better eyesight) may disagree.