In previous versions of Aperture, image version names were used as captions when you shared images to Facebook albums. If the caption in Facebook was changed, the version name for the image would also be changed in your Aperture library.
In Aperture 3.5, images you share to Facebook use the IPTC caption field as the Facebook caption. Changes you make to the captions in Facebook are reflected in the IPTC caption field in the Aperture library.
Note: Facebook albums you already created will not use the IPTC caption field; they will continue to use the version name. Only albums you create in Aperture 3.5 or later will have the new caption behavior. If you want to switch old albums to use IPTC captions with Facebook, remove your Facebook account from Aperture and then add it again. Note that after your Facebook albums resync with Aperture, the history link of your published photos will no longer be available in the Aperture Info panel.