I used this plugin in my tourism web site Seyyah and i will follow the what will google do, and then i will edit my comment.But firstly usage of this plugin is so easy.
Edit: I activated the plugin and i made the google profile, and then i tested the rich snippets but google said like this,
Warning: This information will not appear as a rich snippet in search results, because it is contained in a hidden HTML element. Except in special circumstances, Google won't display content that is not visible to the user. You should mark up the text that actually appears to your users when they visit your web pages.
So, if we dont display on the page, this plugin wont work, so author must say the code for the display the ratings.
I am waiting.