I've been spending more time on Google+ lately (here's the link to my Google+ page). Twitter has been my biggest site of late, with Facebook being a solid second. However, I'm beginning to see some solid value in the Google+ platform.
The main thing I like: larger posting sizes than Twitter. Twitter was designed around SMS limiting factors. The character limits don't, as a general rule, bother me. However, there are times I like the larger posts and Google+ seems to fit the bill better.
Also, especially when compared to Facebook, filtering content and controlling what you see, and who sees your posts, Google+ is clearly better. The interface is cleaner and more straightforward.
It also helps that Google has stated on multiple occasions that it is prioritizing Google+ posts and content. One does need to consider SEO value as well.
Lastly, and most important to me, Google+ is still pretty new. The feeds I see are still quite free of trollish behavior. It's a much more pleasant experience. Will that change if/when the platform takes off? That's my concern. But, for now, it's a fun world with interesting discussions delightfully free of troll-bait.