I think you would find a major discrepancy between "users" and "active users" of Google+. I am one of plenty people who simply registered to see what it was all about. I feel it doesn't offer anything really novel and is just another attempt at World Domination by Google.
Google is actually falling out of favour with me and many others. I feel like they're basically forcing me as a business owner to integrate Google+ with my business (+1 buttons and what not). The consequences of not adopting Google+ as a social media integration tool include major dips in your rankings.
The plus side is that I don't think South Africans are really active enough on G+ to influence rankings much at the moment. It's all fine and dandy if you service a South African market. If your online business focuses on an international target market, though, best you get them +1 buttons sitting pretty on like every page of your website.
G+ is good for 2 things: (1) tech people talking about tech stuff or crap, and (2) humour.
There is no possible way that it can replace either FB or twitter at this stage, and tbh, I don't see it happening.