Google+ was designed from the ground up for a mobile world, as illustrated by its very well-designed app. (No iOS app is available yet, but Google says one is on the way.) The Android app has a clean, straightforward interface that makes it easy to view your stream, manage your circles, see photos and so on.

In addition, the app includes several features not available on the computer version of Google+. You can create a "huddle" with friends -- a group text chat. And you can also take photos with your phone and upload them to Google+, using your phone's built-in GPS to include location information if you wish as well.

As good as Google+ is, there are clearly hurdles ahead. The biggest one is the by-now accepted theory that the value of a network increases exponentially with the number of users on it. With an estimated 750 million members, Facebook has immense value. With only a relatively small number of initial testers at this point, Google+ has very little value. Even when it launches publicly, it will be difficult to catch up.

In addition, the very thing that makes Google+ valuable may well be the thing that holds it back from gaining the kind of popularity enjoyed by Facebook: the way in which you organize contacts into different circles and communicate in different ways with them. With Facebook, you simply accept a friend invitation or issue one, and that's largely it. Google+ requires a lot more care and tending, and fewer people may want to spend their time doing that.