I'm guessing the use-case here is "I have a particularly nerdy observation I'd like to post; I want my nerdy friends to see it, and I'm happy to have random nerds (from Reddit, HN, etc.) wander by and comment on it, but I don't want to bother my family/colleagues/non-nerdy friends with it". Does sharing a post with a circle and "Public" accomplish that, or is it identical with making a purely Public post?
Not just nerdy observations - think about multilingual users. I often want to make a post public in Italian, but I know that the non-Italian speakers who circled me wouldn't be interested...
And I'm sure you're not the only one. I want to be able to post technical (public!) stuff, but keep it from showing up in my 'family' circle. Why that's still not possible is beyond me.
Although not correct, posting to both my 'public' and 'techies' circles would be one way of addressing this issue. But alas, according to you this doesn't actually work that way.
