As you know, title tags are the most important on-page factor. They are given the most weight out of anything on the page as far as the search engines are concerned. So it is a huge weakness in WordPress (and most other blog platforms for that matter) that the post title is used as the title tag, usually with some other extraneous bits added on like the name of the blog.
The plugin now allows you to mass edit title tags for all posts, static pages, category pages, tag pages, tag conjunction pages, archive by month pages, indeed any URL, all in one go.