Yes, this is somewhat embarrassing because I promised that I was done with the updates. But as I said in my last post, Joss Whedon: The Biography contains a number of quotes which I really should include. I've done that, but I also went ahead and made a few edits for clarity and caught a couple more proofreading errors while I was at it.
If you have highlights or bookmarks on your current version, there's no reason to update. Nothing in the new version changes the analysis in any way, it just adds some supporting quotations from Joss or other writers. If your copy is clean now, you might as well have Amazon give you the new one.