If you leave your Kindle on the new software will eventually be pushed to your unit. Amazon doesn’t say anything about what’s new with the update, but Andrys Basten, in her excellent A Kindle World Blog, has this to say:
Menu response is considerably faster now. Page turns are quicker and smooother in response time, for me, and the ‘highlighting’ of paragraphs, which sometimes stalled before completing has been smooth and fast so far.
Tom, Great to read that accuracy of link touching with footnotes seems much better for you now.
Scrolling on Home Screen at least gives a full page, but they seem to make sure that the last part of a ‘page’ in the Kindle Store is repeated in the beginning of the next page, to orient us as to which review we’re reading, in the case of reviews, where I most care about the scrolling. …
Yes, I think this update is to fix reported problems more than anything else.
Her blog post also tells you how to download the update if you don’t want to wait for Amazon.