Aperture

Beyond the usual stability and performance enhancements, Apple's pro-level photo editing tool adds support for Shared Photo Streams, the iCloud-based service that allows users to share photos with any iOS, OS X or PC user. Shared Photo Streams offers support for comments and notifications as well as a web-based client.
Aperture users now have the option to open a file in iPhoto if they so choose.
From the release notes:
Aperture 3.4
What's New in Version 3.4
- Adds support for Shared Photo Streams on OS X Mountain Lion
- A new File menu command can be used to open the current photo library in iPhoto
- Includes performance and stability improvements
Aperture 3.4 comes in at 551MB and can be download through the Mac App Store or Software Update.

Source: Apple
iPhoto 9.4

iPhoto version 9.4 also includes stability and performance enhancements, while adding new card and calendar themes as well as a menu option to open an image in Aperture for more intensive editing.
From the release notes:
About iPhoto 9.4
What's New in Version 9.4
- Adds support for Shared Photo Streams on OS X Mountain Lion
- Comments can now be added to photos after publishing them to Facebook
- New card and calendar themes have been added
- A new File menu command can be used to open the current photo library in Aperture (if installed)
- Includes performance and stability improvements
iPhoto 9.4 weighs in at 757.61MB and can be downloaded via Software Update, the Mac App Store and Apple's Support Downloads webpage.






