Liza Daly reports this in a blog post. According to her the changes are full position syncing across all clients, a new “no distractions” mode that gets rid of the screen color, the ability to make font face and size preferences in both the table of contents view and the reading mode, the ability to adjust width of the text by dragging the right margin, and, among other small fixes, the ability to export the current book to Stanza or Aldiko if you are on an iPhone/Touch or Android.