Only times I visit is when linked, and it's often some OSS-guru who has written something there but I dont ever use it, nor does anyone I know, not even remotely.
We have 50 employees in 3 offices - and have found it to be a really useful internal communication tool.
Each person has a 'private' G+ (apps) account; we share stuff, have threaded conversations, etc - it's WAY better than email for a variety of things, and all the conversations remain limited to people from our organization.
It's totally not what G+ was intended for, but it works well.
Google Hangouts, while being buggy as hell and locking up constantly (at least on OS X), are still unrivaled in the video chat / desktop sharing space.
G+ is ideal for me. I live far away from my family and using Google Picasa I upload photos that I only share with my family.
I don't trust Facebook with my photos. At any moment they could make a deliberate privacy change and expose private family photos to the Internet.
I value that privacy, and although Google might one day make a mistake and accidentally open a security hole, they don't have a history of deliberately reducing users privacy without their express consent.
All my family are signed up, so G+ is no longer an empty ghost town for me. My 'friends' on the other hand are still all on Facebook. I'm just a lurker now on FB.
I have a group of 20 or so friends who all use it because we've got them using it. Every Friday we start a thread and it gets up to several dozen or even hundreds of comments.
These are average, non-technical men and women in their 20s and early 30s mostly.
I have a a couple huge circles of tech and science people that are quite active on G+. It allows for more intelligent posts and conversations than twitter and that's how I primarily use it.
I visit most days. It's like long-form Twitter, so more depth to the discussions. I have some friends on there, but it's mostly to read and lightly interact with industry or interests.
Each person has a 'private' G+ (apps) account; we share stuff, have threaded conversations, etc - it's WAY better than email for a variety of things, and all the conversations remain limited to people from our organization.
It's totally not what G+ was intended for, but it works well.