The main change is the switch to a different storage format for maps. The new format uses a single property per layer with JSON data. This has numerous benefits: easier to recover from errors, easier to edit manually, easier to work with programmatically, etc. (We are doing this change now rather than later to decrease the number of compatibility issues after the release of 9. The less the number of MAP files that use the old format, the better.)
All UI tools working with maps (map window, layout window, all panes) support both the old and new format. Attempting to change a map that uses the old format seamlessly converts it to the new format. Maps in the new format cannot be read by earlier builds.
(Fix) The New Map dialog no longer sometimes writes layers in a wrong order, if there are more than 10.
The background color edited in the Layers pane is always a property of a map. Opening a drawing, image or labels component and attempting to edit the background color will change the background color of a temporary virtual map and will not write these changes to the component. (This is similar to how altering the opacity of such a component using the Layers pane will not save the change to the component - this is a property of a map.)
The map window saves the selection state for layers used by the Layers pane.
The ODBC dataport supports Unicode names for tables and all other database objects.
The Oracle dataport supports Unicode names for tables and all other database objects. (This and previous item conclude the set of changes for Unicode names in dataports. Unicode names are now supported for all databases that allow them.)
The built-in ODBC driver (used to expose data in MAP files to other applications) supports Unicode names for tables and all schema items.
The DBF dataport uses encoding info stored in an accompanying CPG file (used by ESRI products to save Unicode data as UTF-8).
The DBF dataport supports currency values.
The DBF dataport supports memo fields in FoxPro-compatible format. (In addition to memo fields in the original dBase format.)
End of list.