One thing that I dislike about G+, and virtually every other "stream" interface I've seen, is the newest-first chronological sorting. I understand that presenting posts oldest first on something like a blog is totally impractical, but with something like G+, I should be able to view unread posts (or posts with unread replies) and then see just those, ordered oldest to newest, so that I'm reading things in order. Then when I've read the posts (maybe I click on them to mark them as read or something) they disappear from the unread view.

Then there's the issue of posts popping back up to the top because someone replied to them -- that should be configurable, too.