I use my circles and the following of profiles feature for:
A. Getting interesting content in my Home stream, no matter if the ones I follow have circled me or not, unless they only post to "circles". I don't expect anyone to circle me back.
B. I have a lot of Finns (nearly a thousand) in one large circle which I also use for posting in Finnish. On my Finnish page +Gplussa . I have bite-sized circles of several thousand Finns for circle sharing purposes so that newcomers may find people to interact with, in their own language.
C. Communities have replaced Circles in many ways: Starting a community and engaging with people around a certain topic does not count towards the 5000 limit. I own a Finnish "Suomi" community with 20 categories about all sorts of things and an English language "Google+ Helper" community which is all about Google+, with categories of helpful posts for Goobies and old hands alike.