I'm waiting for that ability for Twitter myself. If they could mesh the G+ stream with my Twitter stream, I might be compelled to use it. Buzz got this wrong too, I'm not sure Google understands yet that they can play nice with others and succeed; in fact they have to to succeed. They seem to have their eyes set pretty squarely on a walled garden that can't be extended outside their services, at least so far.
Check out Tweetdeck. It does pretty much exactly what you're looking for with FB and Twitter (and whatever other networks you use). G+ just hasn't opened up an API yet for anyone to tap into it.
I've used Tweetdeck before. Really nice Twitter app, but I don't use FB so there's no need to mesh the 2. My point is, I use Twitter and it serves me well. Without Twitter integration into G+, I have little incentive to use G+. All the friends I care about are already on Twitter, only one or two are on G+. Unless I can read my Twitter feed in G+ in addition to reading my G+ feed, it's pretty useless for me right now. Maybe when they release an API I'll come back and check it out. Thanks for the suggestion either way.