@epsi jokes apart, the interaction felt pretty natural.
All your followings could be categorised into circles where a circle was simply a set. You could follow a person into multiple circles so you could plan a dinner with your family circle and your meeting agenda with work circle. None of them would see your other post because they are in mutually exclusive sets. You should goof around and be serious, all in the same profile.
Posts could be categorised into collections so you could follow a collection instead of the person. Say you are not into the person's political ideas but his cat is super adorable. Follow his cat collection and your feed would only fetch his cat posts
Then there was subreddit style communities where you could join (or not) and engage with people with similar tastes
The integration with hangouts was also good. DMs, group chats and video calls were part of G+ ecosystem.
All your posts containing images would also get saved to google photos.
But google being google, they fucked up every aspect of the social network and killed it.
Twitter is a bad joke, facebook is facebook. Reddit should just die (or not, they need to be contained). I could go on but what is the point of talking about a dead service with no alternative?