One of my largest issues with FriendFeed has been the duplication between commenting on Tweets (Twitter posts) which make up nearly half of all entries on FriendFeed, when Twitter itself is a two way communications tool. The folks at FriendFeed seem to have been listening.
Available now is the ability to respond to Tweets via FriendFeed on both Friendfeed itself and have those responses (complete with @user) posted to Twitter. FriendFeed fans will undoubtedly welcome the feature. Heavy Twitter users are unlikely to switch to FriendFeed full time quite yet (as someone said to me recently: FriendFeed needs its own Twitteriffic), but this is certainly a step in the right direction.