Today, the developer for Calibre rolled out a new version (0.9.20) that adds new book polishing features as well as a several repairs.
Starting this edition, there is an option to smarten punctuation in the book when polishing as well as the possibility to delete all saved settings (available when trying to load saved settings); furthermore, now you can set the application to remember the last used configuration.
The Preferences panel now sports a new option that allows saving backups of files when polishing books.
As for the repairs in this revision, the developer addressed issues affecting mostly the e-book viewer and book polishing procedure. In some cases, the “back” button in the viewer would skip a location, but this should no longer happen in this release. Also, now you should be able to polish more than five books at a time.
For a full list of changes, you can check out this page.