I've seen a couple places say you can't blog without the Ultimate Tag Warrior plugin. But aren't you kind of tagging your posts with the "categories" in Wordpress?
I use a "tag" system on my blog for related posts. I think its great, I find I get alot of clicks on these links to other posts. Its different to categories. Lets say you had a category called "Celebrities" and there were few posts on Angelina Jolie. All your related posts would be other posts about Angelina Jolie. Where, if your visitor clicked on the category "Celebrities" they will only find your latest posts about celebrities in general.
I don't like tag warrior, I've used several programs like that but found if I loaded them up to much technorati just started ignoring my blogs. I just use categories. If you have to write an article about Angelina Jolie simply Post it in 2 categories "celebrities" and "angelina jolie" that way if they want aj they og there if any celebrities gossip they go there. I'd stick with categories I try and stay away from those addons. Just my opinion though . I've also tried simple tags which was relatively the same.
That's how I do things now I'll probably stick with that unless someone has a real good reason for extra tagging plugins.
I use wordpress 2.3 alpha (which supports tagging in the core). I think once you have a good variety of tags, it should be of benefit to visitors, and maybe even for internal linking structure(?). The one thing that has bothered me is the potential for having too many tag / category pages that are too similar. That could be seen as bad by the search engines. I actually made a plugin to overcome this, so that I only index tag / category pages with a certain number of entries on them. I also only use excerpts for tag pages, instead of the full entries.