Embedded in the Microsoft's next OS release, Vista, is a Feeds API. Looks like a centralized combination of feed retrieval tools and subscription information storage.
Upsides: less work for application developers, probably can be easily scripted, wide adoption, Outlook will sync with the subscription store, wide deployment if not adoption
Downsides: information leakage across applications, pre-determined data model with no apparent extension capabilities
Still, you might be able to build the Emacs of aggregators on top of this some day.