I was looking at the latest changed on the Google+ project page
by shear mistake I was using the desktop version (I was using Google+ mobile at the time), and went up a level on the help, and suddenly there was an entry about search on Google+
I tried it, it only is available on jthe desktop version, and it seems to work great!!!
Unfortunately, being hospitalized at the moment, I can't access a regular computer, my Samsung Galaxy Tab 7" which is a great gadget to have in a hospital bed (dont forget to bring your charger), is not the best for the desktop experience. So I can't check this very well - the feature isn't yey avaiable on the mobile site or the Android app. but the one search I did gave back lots of results from Google+ (users whos profiles contain the search term, public posts that match, private posts that have been shared with me that match etc.). It is also possible to save searches.
This is huge, and its silently released. almost everyone has been waiting for this.
a short disclaimer, this might not be available to you, possible reasons:
1. it hasnt been rolled to everyone yet
2. you're using a mobile version
3. it might be available to me because im part of the Google+ Platform Preview so its not publicly yet
still it is very weird that there is no mention of this as a news item on google.