For those on the wait, Apple just issued Digital Camera Raw Compatibility Update 3.12 adding support for the Canon 5D Mark III. You can now process 5D Mark III files in Aperture (and iPhoto for that matter.) The update is available through Software Update in the System Preferences.
I had a shoot this morning and since the update above was not out yet I tethered via Canon’s DPP. Interesting to note that the newest version of DPP & EOS Utility brings along one more small software block, CameraWindow. From what I can tell CameraWindow operates in the background but it adds more flexibility to the DPP/EOS Utility tethering combo. In the past, changing a memory card or loosing the USB cable connection would mean restarting EOS Utility from scratch to get tethering going again. That no longer is the case. Now, EOS Utility opens automatically once the cable is connected and the camera turned on. Changing a memory card will turn off EOS Utility but it reopens on its own when the camera’s memory card door is closed.
Some further testing will be needed to see if this interferes with tethering via Aperture.
On a side note, there seems to be a bug in DPP when showing 5D Mark III raw files. They appear softer than they should. Canon has promised an update to correct this later this month.