I don't have a guide. The beta has all of the original functionality of Data Bridge, but adds MySQLi support for all wizards, Improved file manager for the HTML Editor, and a new Email interface.
So testing would include:
Updating MySQL recordsets, inserts, and updates to MySQLi by opening and changing the connection in the interface
Multiple Insert, multiple update, and Manage Relational Table Server behaviors for MySQLi
DataAssist Pages wizard for MySQLi
SecurityAssist wizard for MySQLi
Email from your web page
HTML editor File manager
Testing any of those with their configurable options and reporting any issues you run into would be very helpful.