Gotta side with these guys. I haven't used the alternative OSes, but, jeez, if I did, I'd want to see all the threads together for the specific OS I was interested in. I certainly wouldn't care if some sub-categories had only a few threads -- that's probably appropriate for what they are.

You know, Linnaeus's taxonomic classification system -- class, order, genus, species? Well, some genera have only a few species -- sometimes only a single species -- but they don't mush the genera together as a result!