I've got all my feeds organized into folders, and usually just scroll through the folder with j/k/space. Is there a keyboard shortcut to go to the next folder (or next folder with unread items)? Shift-J is close, but that takes you to the next unread individual feed rather than the next folder.
Barring this, a keyboard shortcut to expand/collapse all folders would help. But it'd really be preferable to be able to simply "n" through unread stories in collapsed folders without needing to resort to the All Site Stories river.
Good news! I finally got around to this feature and it is now deployed. You can hit Next Unread between folders, and if you are on a folder, shift+up/down now moves between folders. Let me know how that works for you.