This update, recommended for all users of Aperture 2, addresses general compatibility, improves overall stability and fixes a number of issues involving import, web publishing, and the creation and ordering of books
Import
Addresses an issue from Aperture 2.1.3 that prevented the "Do not import duplicates" option in the import window to properly detect and filter out duplicate photos.
MobileMe Support
Addresses an issue that caused JPEG images to be compressed when uploading photos to MobileMe, even when the "Actual Size Images" option was selected.
Books
Addresses an issue that could cause dust jackets to render incorrectly when switching between the softcover and hardcover options with the Stock Book theme.