I think all the social media sites play an important role in generating traffic. Google+ is also one among them, it's on boom now, but Facebook and Twitter are the best still as they are the older platform having number of users and people are familiar with all of their features.
It not only depends upon your sharing. It also depends upon the number of people visiting your shared post and if they are giving it a +1 and also sharing it. And after it if visitors will keep it sharing your visitors will automatically increase.
Yes it is right that Google+ is being used to generate more traffic to a website, because peoples are liking its features so they are getting attracted to it in results Google+ has become the second best social networking site and moving ahead with a great pace in reaching to the top place. And people here are really active they give an instant response if someone is posting a valuable information there.