First off the Bonus Features version will cost you $5.08 USD. (also in 3.49 € & £3.06). Compared to many other products I’ve seen that price is really reasonable.
The first of the bonus features are enhanced bookmarks support that allow you to export them to html or csv as a backup. You can also copy your bookmarks to Google Bookmarks. One of the more important bonus features are that you can lock/unlock your profile to deny access too it but that’s not all… more features will be added over time free of charge to paid customers.
The price is well worth it if those features appeal to you and I look forward to future added features.