When people sing off-key it is unpleasant to listen to. Speaking in absolute terms you don't really have to miss by much. Just a few Hz, but it is enough to make post people cringe.
Google+ is slightly off key. The UI is pretty good, but not use-every-day-good.
On the mobile, the animations ruin the experience completely. I have no idea who came up with the zooming and waving action, but it was a bad idea.
What I use Google+ for the most is to access hangouts. Things have become a bit better, but in all seriousness, every damn time we have a meeting on Google hangouts we start late because someone always struggles to figure out how to join.
Also, the default behavior of the notification thing is just useless. "Person X has shared a post with you" is just about the most useless thing you can tell me. I have lots of contacts. If they post something I don't need to be told explicitly. And if you really have to tell me, show a snippet of what they posted instead of just wasting my time. Bite the bullet: learn from Facebook.
I want to like Google+. I really do. Clever people whom I know created important parts of the underlying technology. But for some reason Google insists on singing slighly off key when it comes to the UI.
Please, someone at +Google
, why don't you try to fix the product.