cut and pasted from the release notes
"Highlights, version 6.4.3
This is a service release providing additional camera support, additional OS support and bug fixes.
• Added support for Mac OS X 10.8 Mountain Lion.
• Preliminary file support for Canon 1D X.
• Tethered support for Canon 1D X and 5D Mark III.
• Tethered support for Nikon D4, D800 and D800E.
• Fixed an issue with QuickLook support."
it works on MkIII as i tried it last yesterday, a friend tried his d800e and it works fine.