Google+, at first glance, appears to have all the prerequisites of a successful social networking site. Central to the page is the by-now ubiquitous news feed, with the ability to share status updates and content and comment on posts. Google also incorporates its +1 button extensively into the interface, allowing you to +1 both posts and responses.
For your interests Google+ offers the evocatively named Sparks; feeds of content relating to specific areas of interest that you can sign up to follow. For example, by subscribing to the cycling Spark you can read and watch up-to-the minute news on the Tour de France, gear reviews from bloggers, and training tips from the pros. Content is filtered to various Sparks via an algorithm, resulting in focused threads with a decent selection of different content (I found that the Sparks algo is too broad in many cases: I had to remove the "Yoga" spark when a celebrity was photographed leaving a yoga class and this content took over it's stream. Sparks are a bit like adding results from Google News about a keyword to your stream: it's a very mixed bag. -Ed.)
Google+ has hung some impressive bells and whistles on the chat experience with Hangouts, where you can gather with up to 10 friends to share a webcam chat. Thanks to an intuitive interface and very smooth switching between speakers, Hangouts have been garnering some fairly extensive praise (1). Once the Google voice and video plugins are installed, all a user needs to do is set their status to "Live" and any friends who are online can join them in a Hangout.
For those without a webcam, Huddles offer a more traditional chat experience. Huddles also comes with an Android app, bringing the group chat experience to your smartphone. A second Android app, Instant Upload, also allows you to share photos and videos direct to Google+ with your smartphone, using predefined default settings to avoid accidental over-sharing. An iPhone app is reportedly awaiting Apple's approval (2)