Among the improvements in the update are additional RAW image support for third-party cameras, improved performance of video playback for recent Macs with Nvidia graphics chips, and resolution for an issue with the Dvorak keyboard layout in 10.5.6.
Also included in 10.5.7 are patches that help resolve issues with third-party network services, such as improved reliability for syncing contacts with Yahoo, and a fix for some problems that could occur when logging into Gmail. The update also improves the reliability and accuracy of several of OS X’s Dashboard widgets, like Unit Converter, Weather, Stocks, and Movies.
Besides the general issues resolved, 10.5.7 includes updates for specific Apple applications, as well. iCal sports improved reliability for both CalDav and syncing with MobileMe, while Mail now has better reliability for syncing Notes and fixes a bug where the BCC field populated incorrectly in certain cases. Apple also improved consistency with Parental Controls and fixed a bug with the system when using full-screen games and Fast User Switching, and also fixed several printing issues, including adding the ability for non-admin users to add and remove printers.
In addition, there are a number of security fixes included in the update, though as of this writing, Apple has not yet updated its security fixes knowledge base article.
The Mac OS X 10.5.7 update is available from Software Update and is recommended for all users running Mac OS X Leopard. A combo updater, weighing in at a hefty 729MB, is also available for those upgrading from versions of Leopard previous to 10.5.6.