Some more tips and tricks for using Google+ search:
* Saved searches are like streams
When you hit the "Save this Search" button, you're creating a new stream that shows up below your ordinary streams. Circle streams are built around groups of people; search streams are built around common interests. So if you save (e.g.) "BBC Sherlock", what you're saving is a stream of people who are interested in that show. It can be a great place to meet people, and to talk about the things you care about.
* You can use hashtags like #plustips
Hashtags are just strings that begin with a # symbol, but people use them to identify subjects or topics of interest. Stick those in your posts, and you can search for them, too. (For example, check out the searches for #plustips or #storycircle) And hashtagging is a collaborative effort: if you add a hashtag in a comment, that tags the post as well.
* You can share searches
The URL you get when you do a search is just https://plus.google.com/s/
<whatever>. You can share this link around and other people get that same search stream; they don't have to be logged in, or even Google+ users, in order to see that link. (Of course, if you aren't logged in, you'll only see public content)
And of course, we're working intensely on making Google+ search a more and more powerful experience. We want to turn these searches into a place where you can find your (and your friends') content, where you can find people, and where people with common interests can meet and talk -- and there's a lot more in the works to make that happen!