Google plus indeed has a big role when it comes to seo especially if you are doing local seo. However, there are still some in depth case studies that need to be done in order to determine what exactly is the benefit of G+ in search. What we are mentioning is a general fact that social signals such as tweets, likes, and plus ones are considered as factors in determining a site's ranking.
Google plus as I can see now only adds to your arsenal of networks for the fact that having a wide variety of social networking accounts will increase your visibility in terms of having a huge network.
