Apple release an update to Aperture today, which brings Aperture to verison 1.5.6.Aperture 1.5.6 addresses issues related to performance, improves overall stability, and supports compatibility with Mac OS X v10.5. This update is recommended for all Aperture users.
The update provides compatibility for Mac OS X Leopard which is launching today.
Yesterday, Apple also release updates to iDVD 6 and iLife '08
Article Link: Apple Updates Aperture to 1.5.6 for Leopard