canuckseo - 7:59 pm on May 31, 2012 (gmt 0)
Personally I don't think reviews have much impact either way. Yet.
We've had reviews on our sites for a while and they have neither positively or negatively impacted rankings. But as we've seen with the new Google+ local reviews are now more important so i'd expect to see them make an appearance sooner rather than later.
That being said, the other advantage to reviews is you can embed RDF markup into your code to display some review and rating info - gives you a little more real estate on the SERP page.