New in Aperture 3 are 39 new editing features and automations. Many of these are nice to have, but don't really impact basic editing needs.
The direct editing brushes are one of the best new features and they work great. These non-destructive brushes allow the photographer to make specific edits to sections of an image. Apple have added a whole new section of different brushes for skin softening, halo reduction, feathering and many others to experiment with. More advanced tools have been added to Aperture such as the Curves Tool, Highlight and Shadow and Edit with Plug-In Menu Item.
Many of Aperture's new tools are designed to help the user make edits and publish while staying in the edit mode. This saves time and steps in workflow. The Batch Apply Adjustments, Live Previews and Variable-Level Zoom are some of the new features that save time and make editing images more intuitive.