With a spate of Web based, RSS aggregation services coming online, it's most appropriate that William Grosso deliver an analysis of the pros and cons of desktop versus server aggregators.
Synopsis? The desktop will be the home of high cost per user services, e.g. tight UI interaction. Server side will rule where aggregating users is important, e.g. metasyndication services.
I'll be interested to see which side wins the bleeding edge extension race. With a decent plug-in architecture, a popular desktop platform would have many more developers. Then again, a server side implementation that presented a really good Web services API (ala Amazon and Google) could be a killer.
Thinking outloud? What if there was a standardized way to represent the reading state of a blogroll? Then you could sync a desktop and a server side aggregator to get the best of both worlds.