GTalk are for me a subset of email contacts.
I'm ecstatic that G+ sharing is being integrated with GReader, because I share a lot on GReader, but not everything I share is pertinent to all of my GReader friends.
Ideally, they'll add a "public circles" feature or something like it, that allows people to subscribe to specific subjects that I define and share to specifically, which would be public, but not pushed into everyone's main timelines.
[Edit: To expand a bit, I hope we'll be able to view those public circles in Reader, since that's the ideal interface for it, and not just in Plus.]
[Edit 2: Thinking a bit more about it, I think I'd prefer to consume all Plus content (except maybe photos, I really like the gallery layout) in the Reader UI. I simply find it to be more efficient.