The broad question I'd ask is:
Is it worth an upgrade for Kindle 1 owners? Is it worth the $100-159 people will pay after selling their Kindle 1?
To me it doesn't seem like it as the improvements are all relatively minor and I have no gripes with the K1 so far. But I'm glad as hell so many people did upgrade since it allowed me to get a K1 for $200 which was my max limit to pay for an e-ink reader.
But as reviews go, I'd say that's a key question to give a clear opinion on why you feel it is or isn't worth an upgrade.