If this is just a preview they should not have opened the gates to everyone.

3) The feature set is almost certainly not what it will be when it goes public.

How is it not public now? Anyone who wants to join can get an invite. Or am I mistaken?

I don't think these are valid excuses for google+ floundering. I think they executed well at the start, but failed to follow through.

At the start it they were all like "Facebook is anti-privacy, we're going to respect your privacy" and then their handling of the "real names" affair brought the cynic out in everyone and we all saw that it wasn't a real alternative to facebook.