1) The user interface is clean and easy to understand.
2) Privacy is step one. The first thing you do is add friends to a Circle. The circle allows you to control who sees each post. Facebook didn’t introduce groups until I had so many friends it seemed to hard to do.
3) Understandible privacy settings. The security settings are relatively easy to understand. An explanation of the circles is part of the marketing. The privacy help section is easy to understand. And, at least for now, there are no 3rd party apps accessing your privacy.
4) Google+ doesn’t own my pictures. I’ve been hesitant to upload my pictures to facebook because the terms of use with regard to intellectual property. Google’s terms of use for PicasaWeb are much more favorable.
5) I see some useful possibilities now that I have the circles in place. Some of this functionality is already available, but merging other google applications with Google+ circles could add power and ease-of-use. Examples:
I upload a photo album to Picasaweb and share it with my family circle. My mother-in-law now goes to one place and see all of the pictures I’ve shared with her. And, she can order prints.
In google docs, I put together a roster for my BBQ=pork awareness group, I share it with the BBQ circle, and the appropriate people have access. Google+ could almost completely replace google groups.
What about Google Voice? At night, calls to the family circle go immidiately to my unlisted home number for emergencies. All others go to voicemail.
Facebook certainly has momentum, but Google has leapfrogged them in core functionality, and the number of GMail users has immidiately given Google a fast start. And if posts can shoot out to a text message, who needs Twitter?