New features: Driver Message Events
Catalyst 5.9 introduces Display Abstraction Layer (DAL) activation of driver message events for notification of controller configuration changes. This feature will apply to all supported operating systems.
Directional Motion Adaptive Deinterlacing Algorithm
Catalyst 5.9 introduces directional motion adaptive deinterlacing algorithm through the 3D shader. The algorithm will detect edges in 5 different directions. This reduces artifacts, and improves the overall detinterlace video quality.
Full release notes can be viewed here. You can grab them here (33.8MB for full download). There's also a Mobility version, you can find this one over here