I had the very first version. I upgraded to the last version before paperwhite because the screen was much better. I upgraded to paperwhite because I saw the integrated light and it's much comfortable than other solutions (and luminosity was an issue eg in planes on older kindle). I may upgrade to the voyage one because it's smaller and i miss the change page button of the older kindles which this one seems to mimic.
So for me it's not that the one I had at each time was too old, or for fun, but because the new version adds something that genuinely improve my reading comfort, while being cheap enough that I don't need to think much about that expense.
Sounds like my upgrade path. I went launch Kindle (for $400!) to Kindle 3 (before it was renamed to Kindle Keyboard) and then to the Paperwhite.
For me, the reasons went: "new," "screen contrast + first-party lighted case," "built-in light + size" in that order.
I've pre-ordered a Voyage. That's in part because of increased clarity and even thinner form factor, and in part because it frees up my PW for my gf, who honestly uses e-paper Kindles more than I do.
