As Chris mentioned on the Google Group, I also found the default view of categories confusing, since they line up with specific topics to the right that may or may not be in those categories.
Unless the format of that can be changed (categories on top of latest), I would recommend the “Latest” view be set as the default. (I changed it to that in my personal account settings.) With a pinned post about appropriate use of the forum, like at the Google Groups.
My preference would be to have some sort of layout that shows categories be the default, especiallky for new users and one can always change this in preferences.