While I'm sure this is no replacement for professional SEO, or hours of web reading to learn what I'm doing, I found this little page, that gives a quick guide to main points on the page, thought it might help a few others.
yes I noticed it only rates you on your specific keyword. I cross tested various websites, including some prolific seo'ers (mentioning no names) and if the gong is wrong, then their websit seo is crap too! It's near enough, IMO, to give a rough guide as to what improvements you can make. SEO isnt an exact science so why should this measurement be any different?