Favrd's best feature is that you can mindlessly scroll through hundreds of random tweets and find hilarious jokes and new people. Favstar might find more stars you have to know what you want to look at before you can see it.

Make the main page a leaderboard for the past two days (maybe call it 'upcoming'), with a focus on bringing to light new and exceptional content.

Reorder the primary and secondary tabs throughout the site so that the left tabs are about recent tweets, middle tabs are about the individual who is logged in and the people they know (i.e. self and community), and the final tabs are about highly starred (i.e. leaderboard) tweets. It would end up looking like this:

Primary: 'Upcoming(?)', Me, My Friends, Leaderboard
Secondary: Recent, Faved By, Given, Popular

The focus would then be on upcoming tweets before community, and finally excellent content that has been noticed and is unlikely to change rapidly - unlike some recent tweets that can disappear unnoticed.

Also, it might not hurt to insert random 5 or 6+ tweets in pages in the same way Digg inserts ads into its pages. This would help to even the playing field and help people uncover under-recognised talent.