Just found a flaw in the All in one SEO pack and wonder if you're aware of it. It occurs if you decide to make one of your Pages a Home page - viz., permanently fixed as the page of entry to your Blog/site.
If you take this move, the All in one SEO pack fails to give your home page any description or keywords. Trying to overcome it by inputting manually your Home page description or keywords results in Posts having 2 sets of descriptions & keywords.
It's a vicious circle...because the options are
i) NO Home page description or keywords = bad SEO,
ii) Every post having the same description or keywords as the Home Page (but admittedly a unique title) = bad SEO.
iii) Every post having 2 descriptions or keyword sets (but its own title) = bad SEO.
Just another of the many trials and tribulations of integrating WordPress into an existing website