One of the main problems with Joomla's built-in SEO is that there are lots of "gaps" where various components don't provide the opportunity to set the browser title, and meta descriptions and keywords.
(Note: Google has announced officially that Meta Keywords are NOT used to influence search rankings, see http://www.mattcutts.com/blog/keywords-meta-tag-in-web-search/ )
e.g. on a category "blog" or "list" page there's no place to add these important bits of SEO information, even though individual article pages *do* have a place to set it.
TagMeta comes to the rescue and allows you to set browser title etc for absolutely ANY URL that's used on your site, including the front page.
It's great to be able to view all the meta information for all the pages that you have set it on, in one place. You could even use this to set the meta information for individual articles rather than setting it in the article itself, but you can do it either way.
Something I found out the hard way, as someone else pointed out in an earlier review, is that when you enter the URLs for matching, that the URLs use "regex" syntax, and also don't have "http://" in front of them.
So, if you want to match an exact URL you need to put ^ in front of it, and $ at the end of it, and don't forget the leading slash... like this:
If you just put "forums" as the URL, then this rule would match any URL that contained the word "forums" in it, e.g. you might have an article with that in the title and therefore URL. So the ^ and $ "anchor" the start and the end of the string so that it doesn't do a substring match.
Therefore for the front page, the best URL to use is ^/$ which will match only the very front page and nothing else.
It would be great to have an option when you are creating each rule, to use regexes, or "starts with", or "contains", or "matches exactly". That would make it a lot easier for most users who don't need the power of the regexes.
As someone else mentioned, some characters in URLs need to to have "\" in front of them in order to work, most notably "?". There are others too, like "." that otherwise actually matches *any* character, not just a dot.