wtlloyd said:
Alright you mugs, remember you read it here first!
http://www.fredmiranda.com/forum/topic/1344561
Hmm, they didn't mention firmware 1.3.3 for the 5D3 is available from the same place.

(Actually, a forum member there beat me and posted about the 5D3 in a post to the thread)
http://www.cla.canon.com/cla/en/consumer/products/cameras/eos_cameras/eos_5d_mark_iii#driversAndSoftwareTab
For the 5D3:
Changes Firmware Version 1.3.3 incorporates the following improvement and fix. 1. Improves the AF controllability when shooting in Live View mode with a wide-angle lens (fixed focal length or zoom). 2. Corrects some incorrect indications on the "English" and "Russian" menu screens. Firmware Version 1.3.3 is for cameras with Firmware Version 1.2.3 or earlier. If your camera's firmware is already Version 1.3.3, it is not necessary to update the firmware. When updating the firmware of your camera, please first review the instructions thoroughly before downloading.
Note: Once the EOS 5D Mark III camera is updated to Version 1.3.3, it cannot be restored to a previous firmware version (Version 1.0.7 through 1.2.3).