As well as liking cards, you can now also favorite people and streams.
This is done by clicking the star on a stream or profile page.
But whereas likes are a lightweight way of acknowledging what someone has written, favoriting an entire stream or a person has an additional effect.
Now on the main page that shows the latest updated streams, new streams, general thoughts and the fire hose, you can now choose to filter just by favorites.
When filtering by favorites, you'll only see content from streams you've favorited and from people you've favorited.