I managed to add this to one of my sites. I can't tell for sure that it did anything good to my rankings (I did too many changes at the time) but I can guarantee You that someday it will. Here's why:
- You show search engines that You put effort into creating Your site,
- structured data is yummy,
- someone, somewhere, someday (most probably already) will scan web for structured data and will use it in some way, potentially linking back to You.
Notice: I used GWT to verify validity of code on product pages, however GWT told me that it didn't found any rich data on the page. As I later found out it didn't mean that my code was invalid, but that GWT decided that the page isn't interesting enough to scan for structured data.
