Compared to dedicated feed readers, one of the major disadvantages of Safari RSS has always been the lack of an ability to set update intervals or article expiry intervals/times on a per-feed basis. Setting your global update interval in Safari to 30 minutes might be appropriate for high-volume feeds, but it places an undue burden on sites like Mac OS X Hints which are only updated once a day.In Leopard, RSS reading functionality is no longer built into the Safari application itself. There is a system-wide RSS framework called PubSub (Publication Subscription) to which various applications (Safari, Mail, even Xcode) are subscribed as clients. This has a number of advantages. An application called PubSubAgent runs in the background and updates feeds even when client reader applications are not running and (of course) feeds to which multiple applications are subsc...