The ability to take something like most forum packages “New Posts” data, and distribute it over RSS.
Could you imagine, tracking your favorite forums over an RSS Feed reader? Just click the link in your feed reader, and voila: view the whole thread in a web browser :-).
Just looking at the ‘Google Reader in Plain English’ video, makes me wish I could stuff all the sites I frequent into ONE place; I haven’t checked RSS feeds in centuries but forums, every day baby…