My client has been using 4Sprung's Advanced SEO Suite since December and they love it. It really helps them figure out what is needed to make their site more SEO friendly. I'd highly recommend this addon to anyone that wants to improve their SEO.
We've had great success with this on various sites as well.
Thanks FDG web and Brandon we constantly improve the add-on further, please have a look at our change log and make sure you have the latest version. Feel free to email any feature suggestions you have.