[theBobMcCormick]

I'll certainly use circles if enough of my friends, family, coworkers, etc. start using Google+.

If Facebook had that feature, I'd be using it frequently to post geeky technical stuff to my work friends without boring my non-tech relatives, posting pictures of my kids to my relatives and close friends without boring my work friends, posting politically charged stuff to only those friends I know are on the same side of the political fence, and posting about my side business without my boss and my coworkers being able to read it! :-)

As it stands now though, most of the people I know are on Facebook, relatively few are on Google+ (yet at least), and I just end up occasionally posting fairly bland, watered down stuff that's unlikely to bother anyone, etc.