I think for big boards it is an issue that your board is very large. So you have to scroll a lot to get to the target forum you want. Or when you have 50 posts each thread as default, it takes so much time to scroll.
I thought an add-on for this problem would be great. So when this add-on is installed, an option for admins to choose the "scrolling attitude" would be great.
For example scrolling attitude: category.
So with each scroll (1 time wheel moving) the page on forum index would scroll "from category to category". So if you have 10 categories, with 10 scrolls you are on bottom of the page already, instead of massively scrolling down.
Or scrolling attitude: title bar
Of course support for custom add-ons would also be great, like xfrocks' widget frame or AndyB's sidebar position. So the scrolling attitude (when option enabled) would scroll from title bar to the next title bar. That means from 1st category title bar to the next title bar. This could be the title bar of a sidebar widget (AndyB or xfrocks) or the next category.
Or scrolling attitude: postings
So with each scroll it would scroll to the next posting.
Like when you read a pdf. You can scroll normal, so a fluid scrolling. Or a scrolling from page to page, in our case from posting to posting.
You could add so many scrolling attitude and each admin can decide what is the best for himself.