The benefit to it is really just about having additional web presence and additional ways for people to find you. It's also obviously owned by Google - and your Google+ profile will often show up on the first page in search engines, and if people click it and your website is listed there, it's an additional way to get exposure. So I would say it's somewhat important (it's something that's nice to have), but less important compared to taking the time to really get to know and use at least one social media network extensively and putting the effort in engaging people and staying active on it.
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