First, they’re adding more data to the @YOURNAME tab so you can easily see who is reTweeting you along with messages directed at you. It also lists Tweets that were favorited but does anyone really use that function? I’m a big Twitter user and don’t think I’ve ever favorited a Tweet. This tab will also drop you a note if someone follows or lists you.
Next, they’re adding a whole new tab called Activity. Activity should mean everything that happens in your account but it doesn’t. This new tab will show you what the people you follow are up to including their favorites, new follows and reTweets. Here’s the example from the Twitter blog: