In my usage G+ is not at all like Facebook.

The big difference is that Facebook is highly oriented towards "small circle of people I know in real life" and slowly opening up things to be more public.

G+ is highly oriented towards public with features to allow more private sharing. It's more like Posterous, really, than Facebook.

The concrete difference is that on Facebook I follow friends and coworkers, on G+ I follow Scoble, Tim O'Reilly, Alton Brown and other people who write interesting, public posts.

My G+ usage is pretty orthogonal to Facebook usage and is more like following blogs in an RSS reader.