Just a small thing.
The plugin outputs the review rating as:
<div class="blog-yumprint-rating" itemprop="ratingValue" content="4" bestrating="4" style="display: none;">
But as per Google's rich snippets troubleshooting page:
the content must be visible to the user (ie. you can't use display:none).
In stead, as per Google's Rich snippets - Review ratings page
You should use
<meta itemprop="rating" content="4.5" />
Which will still hide the content, but in a Google-safe way.