As Google changes the rules these apps tend to fail and actually harm your rank.
This is why you should keep up with SEO Forums and spend way too much time on this.
My advice is to forget SEO and go for quality products folk want. Also, in the USA shipping costs can undo a sale. Try to strike a balance on shipping. Make it a non-profit part of the sale.
Does anyone have any experience with online reputation management software that helps SEO for your website and directs reviews to your website?