Web pages that implement this kind of clear communication have a dramatic advantage because the search robot does not have to guess at the purpose of the page it is visiting. This saves time, prevents confusion and enhances the perceived value of any of your pages.
The main areas that structured data will help your site are:
2014 Study: Pages With Schema Markup Rank 4 Positions Higher in Search Results [Searchmetrics Study]
While there is no direct evidence that supporting structured data will improve page rank, it will definitely make your listings stand out in the results and has been proven to increase click thru rates.
Pages With Schema Markup Rank 4 Positions Higher in Search Results [2014 Searchmetrics Study ]
Here is an example the kind of enhanced search engine results for a product that implements the correct structured data. (Note: Reviews summary, price and stock level.)
Initially the work required to implement Schema (structured data) seems daunting, but it is worth the effort. There are many online resources that will make your work easier including some good Magento Extensions.
Once you have successfully implemented, you can test your pages using the Google Structured Data test tool. Here is an example of the kind of result you can expect.