I think it would be cool to have subforums. That's really the only thing missing from smf. I have alot of forums take up space on the index but would save space if they were in a subforum because they go with that category.
SMF already has subforums built in. All you need to do is set the parent forum. There are subforums on this site by the way.
On SMF they are called child boards.
Where do I do this?
Add a new board and on the Drop down select "Child of".