By now many of you have already done the upgrade to 10.6.4. From what was mentioned in the update info, most of the changes were security fixes, and small bug fixes throughout the OS. However, there are a couple of improvements for Aperture users, the main one being expanded tethered shooting support. According to Apples website, 10.6.4 adds tethered support in Aperture for additional digital camera models. From the reports we are hearing this includes the Canon 5D MKII and the Canon 1DS MKIII.
The update also addresses IPTC computability issues, and adds RAW support ( throughout the OS ) for additional digital cameras, though we have yet to see an updated list. This is exciting news for any Canon shooters who have been frustrated by having to contend with Canons proprietary software to handle tethered shooting with certain cameras.
As reports come back ( or we see an official list of supported cameras ) we will be sure to keep you posted.
UPDATE: This just in, we are hearing reports that the changes to the metadata computability issues in the 10.6.4 update have to do with how Aperture exports IPTC metadata so that 3rd party applications can read it. We are also counting up all the cameras that Aperture now supports for doing tethered shooting, and although all the results are not quite in yet, it is safe to say that A3 supports at least 20 more cameras for tethered shooting than LR3 does!