I tested some plugins, all best plugins for SEO. This plugin NOT write keywords for articles and pages, Meta title is fine but description and keyword don't work. With the platinum seo (a "updated version" of All in one SEO, For me this plugins is the same as AIOSP) the same problem happens. When I install SEO Ultimate everything is fine. I tested this with SCRIBE SEO and viewing the page source of my articles and with AIOSP and PSP is NOT ok, but with SEO Ultimate is OK. Scribe SEO will tell you if you have custom titles, meta description and keyword for your article.
Try this and convince yourself!
PS: Sory for my english !!!