I just converted everything on my site from categories to tags. I’ve implemented Ultimate Tag Warrior and then backed up my database and converted using the unproven “cat2tag” feature. It seemed that all went ok and I dumped all posts back into the default category. I then removed the rest of the categories and changed “Filed Under” to “Tags”.
All seems well. Maybe some more tweaking, I think I’ve tagged most of the posts. I had a lot in the default category and I had to tag all of them; I think it was about 200 posts. I’ve also implemented a tag cloud in the side bar as well as moved up the search box. Believe it or not, I often come back to my site to find something and I hate scrolling halfway down to find the search box.