The Personal Document feature is really cool. One of the things I had been hoping for was the ability to archive as well as sync (farthest page read and highlights and notes) in files other than books directly purchased and downloaded from Amazon. Most of my recent books were purchased and downloaded from Amazon. However, occasionally I buy a Topaz book which I then deDRM and convert to mobi so that the text reflows like a normal mobi book. This makes it a heck of a lot easier on my eyes. In the past that would have caused the book to not be syncable because it was modified. I also have tons of books I purchased from other stores and in other formats This allows me to archive and sync them too!