* You can now specify the background opacity (--export-background-opacity or -y).
* If no background color (-b) or background opacity (-y) specified, the values from the document (sodipodi:namedview) are used.
* You can now export an area corresponding to a single object by specifying the ID of the object with the --export-id or -i switch, for example:
inkscape -e mypath.png -i path966 mydoc.svg
* When exporting with -i, you can add --export-use-hints or -t to tell Inkscape to use the filename and DPI export hints stored for that object when it was last exported from the GUI. For example,
inkscape -i path966 -t mydoc.svg
will export path966 to the PNG file with the same filename and resolution as you used for exporting it from wihtin Inkscape, so you don't need to specify them on the command line.
These changes (see the man page for full details) allow you to easily script exporting parts from complex documents and to better integrate GUI editing with command-line use.