The best feature on Twitter is one you probably don't use. I'm talking about Favoriting, the act of adding a star to a tweet that you like. It's going to be huge.
Twitter added two new features today, an @usernames tab and an activity tab. The @username tab will show you all the activity centered around you—your new followers, which of your tweets were retweeted, your @ mentions and which of your tweets were favorited. The activity tab shows the same stuff, but about your friends, which tweets they favorite, who they follow, and more. It also gives you the option to see all their recent favorites.