Since I work at an SEO software company, the choices we make when it comes to SEO software for our WordPress site are very important for us...as they are for everybody.
We have just completed implementing this SEO plugin at http://theseosystem.com.
We used to recommend the All in One SEO Pack but Yoast came along and has make things even more simple.
Make sure that you take advantage of the social media features of Yoast as social media signals are critical in today's world of search and social engine optimization.
The most important example of this is to take advantage of Yoast's simple Google authorship features.
Hope this helps you all out there make your decision.
In summary, 5 stars!