I was recently invited to join Google+. I'm using both Google+ and Facebook now, although the latter more than the former. My Google+ circles are gradually working up to actively using Google+, and so far my circles are a mix of Facebook and Twitter friends (I replied to a Tweet asking who was on Google+).
This article thinks that Google+ isn't a good personal branding tool, and I'm not sure I agree. I love the Circles feature, because it lets me control who sees what. There's a marked difference between my LinkedIn contacts and my Facebook friends, and a marked difference between what I post in both places. LinkedIn is professional; Facebook is social. It's the same way I have Twitter set to only post my #in tweets to LinkedIn; my professional contacts don't necessarily need to see that I replied to Aziz Ansari about the premiere of the fourth season of Breaking Bad. Circles helps me compartmentalize.
One feature that I'm really curious about is Hangouts, where you can use a video conference to connect up to 10 people. I don't have occasion to use it yet, but I think it could be a great personal or professional tool.
The author and I are on the same page in that we both think Google+ can be a useful supplement to your personal brand, but it's still best to cover all bases. The author seems a bit more negative about it than I am, though - I'm definitely curious to see what features are added.