Apple released an update for Aperture 3 today. This update includes support for Mountain Lion and a few performance tweaks. Here’s the full summary of the update.
Supports compatibility with OS X Mountain Lion
Addresses issues that could affect performance when entering and exiting Full Screen mode
Auto White Balance can now correct color using Skin Tone mode, even when Faces is disabled
Projects and albums in the Library Inspector can now be sorted by date in addition to name and kind
Includes performance and stability improvements
The update weighs in at 555MB.