I used to use SEO Pressor, but WP Easy Wordpress SEO is cheaper and does WAY more. See my sig for link, or google it
If you are looking for free plugin then seo all in one is best and if paid then seo pressor is best cost nearly 47 USD
Yes, it's very good, but with 100% score on WP posts it creates double h1 tags. Pages are ok with 100%