This feature is directly based on a request from a user - folder level item viewing. What does that mean? Well, it's pretty simple. If you select a folder, all the items for that folder will show up in the item view. I have to tune this some; the item view isn't showing the originating feed at this point. That's why it's a dev stream only feature :) I'll get that fixed today.
Update: I've added the feed information to the table view when you select a folder.