Tonearm - Google Reviews don't apply to what you're asking about. You are correct... they are for local business listings.
I've recently been doing some test searches for a manufacturing client, and from what I've been seeing, reviews on a site are more likely to rank you for "productname reviews" than for "mysite reviews", so this may not do what you want unless your sitename and the name(s) of the products you sell overlap. It depends, of course, on what vocabulary you put on a page and how you emphasize it for search.
In my test searches, Amazon pages were ranking, as the manufacturer has no review pages of its own. Amazon generally has its top reviews (or top review excerpts) at the bottom of the product page, and then these same reviews with additional reviews on separate review pages. Obviously, they've got custom software to do this. I don't know whether there's available code to build something like this for whatever shopping cart you might have. I also suspect that Amazon may do a good job at editing its reviews... fixing typos, etc, but I'm not sure of that.
If you put your comments somewhere else, like Disqus or Facebook, they may or may not help your pages, depending on how you do it and where you put them. Several years ago, on SE Roundtable, Barry Schwartz published a method for allowing Google to index Disqus comments, and I'd bookmarked it. Here's the link to Barry's article. I don't know how easy it would be to adapt to your setup.... Can Google Index Disqus Comments? No But Here Is How. Sep 29, 2011 - Barry Schwartz
... to a user, the comments seem to be fully powered by Disqus. But I manage the comments via the API but on the CMS backend we built. So when I remove a comment for spam, it removes it from both the search engine's view and user's view.
Let me say that this is not cloaking or anything like that because users and search engines are seeing the exact same content.
If you follow all of Barry's links, etc, you'll also see that Disqus offers plugins for Drupal, Blogger, etc, and has a "Data Synchronization Guide". I assume that Facebook does not.
I should add that some months back Barry removed this data synchronization to Disqus because he wanted to remove the comments from the Google index. He'd come to feel that some of the distracting user-generated content was creating a Panda problem for him. So, if you do have user reviews, I assume they need to be well-moderated. I'm not sure what the user expectations on this generally are on e-commerce reviews.