Aperture 3.3 and iPhoto 9.3 support unified photo library format

The newly released Aperture 3.3 and iPhoto 9.3 use a unified photo library format which you can open from both Aperture and iPhoto. By sharing the same library format, you can open the same library under Aperture and iPhoto without the previous laborious import/export procedures. Faces, Places, Smart Albums, slideshows, image adjustments are now shared across both apps.

Apple has released a detail technical document about using this unified photo library in Aperture and iPhoto.