Version 10 is not a massively changing release, as well as the new XML API which doesn't effect the rest of the forum engine, the main change is in the way configuration data is stored in the database and then read in in the includes/global_variables_inc.asp file.
With the new configuration settings engine configuration data will be stored in a single table with just 2 fields (Option_Item and Option_Value). This allows many more configuration options to be added, and without having to keep modifying the database to add new configuration options.
This means that allot of configuration options previously found in obscure settings files that needed a text editor to change will be available in the online admin area.
The online Admin Area is were you will see the most changes with lots more configuration options such as:-
- Setting username and password lengths
- Setting the Page Encoding
- Left-To-Right or Right-To-Left language settings
- How session data is stored (DB or memory)
- Cookie settings
- Enabling and disabling Guest Sessions
- How often Tracking Codes are updated
- RSS Settings (How many items to display, Time-To-Live, etc.)
- Search Settings
- Reverse Post Order
- Private Messaging Settings
- Calendar Settings
- Changing the mail server port from the default port 25
- Setting up the Existing Member API
- Enabling the new HTTP XML API
- + Many more configuration options
As far as the frontend goes it's many fixing issues and adding a few smaller features like the most ever number of users online and displaying forum moderators.