We love this plugin and I have it on quite a few client sites. However, I was just reviewing the code and found no Schema markup, which is why I adjusted to three stars.
It does pass the rich snippet test for a single review, but when displaying all the reviews (either in full or excerpts) on a page, running it through Googles Rich Snippet tester warns that there's no compliance for showing aggregate reviews correctly, and warn it rich snippets will not show for that page.
Lots of potential here, though and I do like the interface and ease of use for the shortcodes, etc. so I hope the new version of this (still coming soon?) will be an improvement.