That sounds about right to me. Though obviously there's a spectrum there. One assumes Google's hope is that as the adoption grows, the "None of my friends are on" problem will progressively disappear. When some of your friends are on G+, you'll start posting stuff there. And until then it's a cool way to learn about the restaurants frequented by Lennart Poettering.
When it first launched all of my friends joined and began to post, including the many without facebook accounts due to tight gmail integration. But within a month or two almost all of them stopped posting. Whether they will come back is the question, a profoundly different one than whether they will join at all.
