It is absolutely free, and ad-free. It allows you to browse and view all available SharedPreferences XML files on the system.
Using a rooted phone with the super user app, you only have to confirm root access a single time, then you can browse the Shared Preferences as much as you want. The main screen lists all installed packages that have a shared preferences directory. After choosing a package to view, you are presented with a list of all of that packages SharedPreferences XML files. Next you may select one of these XML files to view its contents. Hit the back button at any time to return to the previous screen.
Future versions may include an XML editor and the ability to modify the files.