Canon has made available for download firmware version 1.2.3 for the Canon EOS-1D Mark III and firmware version 1.1.2 for the Canon EOS-1Ds Mark III.
The Updates allow the user to select AF points directly with the Multi-controller instead of the Quick Control Dial or Main Dial and additional ways to apply exposure compensation. They also promise to: "improve the stability of AF accuracy in AI servo AF mode when shooting extremely low-contrast subjects.
Further details of the firmware updates can be found here: