No, I don’t, and here is why:
Over specialising categories is a common problem that manifests itself differently in communities old and new. It most commonly manifests as a gigantic front page, filled with every possible permutation of the community’s general topic. A community about games might have separate categories for firstperson shooters, thirdperson shooters, side scrollers etc, where they would better be served with either a category marked “Shooters” or simply an overarching category marked “Games”.
Essentially you shouldn’t have a ton of categories. Users want simplicity, and playing the “is this animal, vegetable, or mineral?” game on the front page is not fun or simple. A basic list of the last 100 topics is, though… until you get 100 new topics every few hours.
One advantage of tags is that they are lightweight and can be mostly ignored. Categories are like walls. Four walls and you have a nice house… 30 walls and you have a maze.