I hacked up Journalized-Blue‘s index.php to replace the category listing with Felix Wong’s tags plugin. I still need to grep the rest of this theme for categories and fix them as well. Then I’ll have to see which of the rest of my themes are worth the effort. (I guess it’s not that tough to add tags support, it’s just a matter of finding all the places where categories are listed in all of the theme php files.)
I should probably also be a good citizen and post the modified themes.