I don't tend to buy many commercial Joomla extensions but this is one that I think is well worth every penny.
I love the Meta Tags Manager that lets you view all the tags for every page on one screen so you can easily see what needs doing and cut and paste as necessary. The only improvement I would suggest here is a character count on the description. Actually I did a mod to the default.php page to make all the data boxes bigger (50 wide by 3 rows) so that does give me a rough indication of the description length.
Overall though, a great extension that I will be using as standard on every site I develop. Thanks.