Along with the introduction of a fresher look and sidebar navigation, the biggest change, and perhaps the most welcomed is the introduction of duplicate detection, a long sort after feature. The problem with FriendFeed to date is when big stories break, often many people share the same link, creating a noisy life stream full of duplicates. Now when multiple friends share the same link, the set of duplicate entries will only show up once in your feed. From what I can gather, this applies to the same link only, as opposed to the same story, so there will still be some duplication, but it’s a vast improvement from the previous situation.
Included also in the release are friend lists to help users organize their subscriptions into groups, and the ability to see what other people see, both features rolled out during the beta testing stage.
Full details on the FriendFeed blog here.